Legend has it that in a fit of remorse Henry Pomeroy either killed himself or had himself bled to death. One of the things that happened after a suicide was that all property reverted to the Crown.  The lands of Berry Pomeroy did indeed revert to the Crown, either because of the manner of his death or because he was attainted for treason.
Henry Pomeroy  having escaped the king's justice meant that the Kings justice fell on his blood brother his brother.  Josceline  was tried at Winchester on 8 April 1194. Everything he had, property, status, title, everything was lost to him and his heirs.  His sentence for High Treason compelled him to become a monk at Forde Abbey. Being forced into a monastic house was a most unusual punishment for treason, the usual punishment was execution.
He went to Forde Abbey where he remained as a monk until , in 1199, he learned that Richard I was dead. He immediately left Forde and settled at his estates in east Devon at Payhembury
Joscelin Pomeroy's 'punishment' seems unusual. It suggests to me that their relationship to Henry I was in their favour. Richard I  was a grandson of Henry I & was directly related to the Pomeroys, their mother being the illegitimate daughter of Henry I . 

A ) MIGHT the legend of suicide have some foundation in truth.

B ) the sentence  metered out to Josceline was lenient because the Pomeroys and king Richard had the same grandfather a. The Pomeroys were descended from the illegitimate children of King Henry I , and as such  had status .

C)  Having read further about attainders it seems more likely that this was a case of guilt by association. Joscelin, living  in East Devon,  far away from Cornwall and St Michael's Mount,  may not have been drawn into his brother's treasonous activities, BUT was considered guilty because by association, by tainted family blood. 

To plot against the king was treason which was punishable by death. Thus it might be considered an act of suicidal recklessness.

Or was suicide by ones own hand preferable to being hung drawn and quartered..? 

Could the legend of suicide be a metaphor for treason  OR could the legend of suicide have been designed to hide a worse crime, that of treason. ?

Which ever it was the results were the same. Attainting. All property and status was confiscated and returned to the Crown for several generations.

[ attainted; attainder was the metaphorical "stain" or "corruption of blood" which arose from being condemned for a serious capital crime (felony or treason). It entailed losing  one's life, property and hereditary titles, and the right to pass them on to one's heirs.

Both men and women condemned of capital crimes could be attainted.

On 17th April 1164 King Richard I , who had lived all his life in France and spoke almost no English , was crowned at a 2nd coronation at Winchester. Within the month he had left England on Crusade .

King John, who was a nasty piece of work, unstable, vindictive and deeply vicious, assigned to the custody of the Berry Pomeroy barony to William Brewer, a prominent but deeply unpopular administrator and judge , & major landholder who founded and endowed three monasteries including Torre Abbey, on Torquay in 1196.
The custom of sending sons to be brought up in another family of equal status makes likely that this man might have had the Pomeroy heir Henry (3) as ward. When Josceline was forced to become a monk it seems possible it was by way of penance, to make some amends for the 'mortal sin' of his brother.

 It would appear that they were both attainted and lost everything for the treason   Could the ruthless warrior Richard the Lion Heart really have been that generous, because it was certainly a most unusual punishment for High Treason

There is another possible reason for the leniency. Family connections. King Richard, Henry and Josceline Pomeroy all shared a grandfather, they were cousins and Royal Blood flowed in Pomeroy veins.

 Evidence 2] 

When King Richard died unexpectedly in 1199 Joscelin immediately quit the religious life. This suggests that the attainer on him and his lands was reversed. King John returned to him the properties he had at Tale and Payhembury, near Forde Abbey, which were his due as 2nd son. There he settled and we hear no more of him. Whether he married and had children is unknown.

When the 2nd Henry Pomeroy's widow Rose or Rohese remarried in 1200 her future husband, John Russell of Kingston Russell, had to buy her from the Crown. The Bride Price was 50 marks of silver.

Evidence 3]

The Berry Pomeroy lands having been attained remained the under the control of the crown and the next generation the 3rd Henry Pomeroy paid 700 marks for his livery and the king's benevolence. This Henry made a prestigious marriage to Alice de Vernon daughter of William REVIERS, 5th Earl of Devon.

In the following generation, yet another Henry Pomeroy,  the 4 th of 9 Henry Pomeroys , also had to pay a large sum, 600 marks, for his lands in 1211. This Henry married well taking as wife Johanne Vautort of Trematon sister of Roger de Vautort.The Feudal barony of Trematon  was one of the three feudal baronies in Cornwall had its  caput at Trematon Castle, near Saltash . In 1166 Trematon comprised 59 knight's fees, and 59 separate manors. Roger III de Vautort died childless  died 1274, declared insane for disposing of most of the family's holdings for next to nothing leaving vast debts. 

In those highly religious times suicide left a stigma of a family name, a mark of cowardice. That indelible stain lasted for several generations. All of which makes Joscelin Pomeroy's 'punishment' seem unusual and different.  However since being attained affected an entire family it seems more likely that Joscelin was punished for being a traitors brother. Collateral damage.

With only title of Baron, the lowest rank of English nobility, and no other title by which they might re invent themselves, the Pomeroy family do appear to have suffered for several generations. They paid a heavy monetary price for at least 3 generations yet that bill of attainder could be reversed at the stroke of the king's pen, all forgiven and forgotten. Indeed it was in Joscelin's case, for when Richard I died in 1199 Joscelin immediately left Forde Abbey and retired to his Payhembury estates.

There is another way to look at the legend. To knowingly plot with someone like Prince John against the sovereign, the warrior king Richard, was tantamount to killing oneself.  The punishment for treason was death. So could suicide by ones own hand have been preferable to being hung drawn and quartered..? 

 OR yet another thought - Could the legend of suicide be a metaphor for treason or was the legend designed to distract from Henry's treason. 

Which ever way is was Sir Henry was almost certainly dead around the same time his brother was tried for treason in the spring of 1194. The reason we know this is because in that year, 1194, the his son had to pay a huge sum of 700 marks to the Crown for his  'livery of his lands'.

Which was the greater crime - self murder or treason?

'' Medieval accounts of suicide describe it as a private deed which its perpetrators did their best to conceal. It was often difficult to prove, and commonly the subject of discreet allusion by means of euphemism, metaphor and circumlocution. 

Suicide was widely felt to be too terrible to talk about, and though the word suicida was coined as early as c. 1178, it was not accepted into general use, and seems to have vanished until well after the end of the Middle Ages.

The English crown was unique among medieval monarchies in its success in imposing the principle that any violent death within his kingdom was prima facie a crime against the king and therefore a matter for investigation by royal justice.''

Alexander Murray Oxford, Oxford University Press, 1998, ISBN: 

Richard Carew in his Survey of Cornwall 1602 relates this thus.

St Michael's Mount captured, 1193 Sir Henry de la Pomeroy captured the mount, on behalf of Prince John, in the reign of King Richard I

Until Richard I raigne, the Mount seemeth to haue served onely for religion, and (during his imprisonment) to haue bene first fortified by Henry de la Pomeray, who surprized it, and expulsed the Monks: howbeit soone after, when hee became ascertained of his Soueraignes enlargement, the very feare of ensuing harme wrought in him a present effect of the vttermost that any harme could bring, namely, his death: 

 whereon, the olde cell and new fort, was surrendred to the Archbishop of Canterbury, in the Kings behalfe.  Thus Houeden reporteth.

 But the descendents from this Pomeray, alias, Pomeroy, make a somewhat different relation of this accident: for they affirme, that a Sergeant at armes of the Kings, came to their auncestour, at his Castle of Bery Pomeroy, in Deuon, receyued kind entertaynment for certaine dayes together, and at his departure, was gratified with a liberall reward: in counter-change whereof, he then, and no sooner, reuealing his long concealed errand, flatly arresteth his hoaste, to make his immediate appearance before the King, for answering a capitall crime. Which vnexpected and il-carryed message, the Gent, tooke in such despite, as with his dagger hee stabbed the messenger to the heart: and then well knowing in so suparlatiue an offence, all hope of pardon foreclosed, he abandones his home, gets to a sister of his abiding in this mount, bequetheth a large portion of his land to the religious people there, for redeeming his soule: and lastly, causeth himselfe to be let bloud vnto death, for leauing the remainder to his heire:  from which time forward, this place continued rather a schoole of Mars, then the Temple of peace.    ( ?? A school of War rather than peace?)