Hello we have reached Patterns/Spacing here today. Most would probably consider this more easy to mod but whilst that can be seen as such, modding spacing can be much more harder than you think it is.
So without further ado let's get on to something!
(Disclaimer: This is how I would mod these things)
Differentiating Patterns/Spacing problems and Rhythm suggestions
Spacing problems are by far the easiest thing for a mapper to do within a mapset. Whether it is a Distance-Snap error (DS) on a lower difficulty or Just simply misplacing an object on the other side of the screen on a top difficulty that is 1/4, it is one of the more common mistakes you will see on a map.
Similar cases around Patterns in a map ^ since these usually go hand and hand together when it comes to making mistakes.
So with that said, what would be considered a Major Spacing/Pattern Issue?
Jumps that don't fit with snapping choice or anything else within the mapset and obviously is a mistake.
Example: Song is mostly 1/2 sliders and any 1/4 circles are stacked with the 1/2 slider, and then suddenly you have a moment in the map where the 1/4 circle is not only not stacked, but mapped as a 1/2 jump. Rest of the mapset continues on and this is the only moment it happens.
Major spacing/pattern inconsistencies that there is no sense of what any pattern is trying to do and can lead to it essentially following nothing.
A mistake that can negatively cause a bad gameplay experience.
What would be considered a Minor Spacing/Pattern Issue
Jump is inconsistent with the rest and mapper cannot argue with it. Usually not that harmful and generally forgiveable.
Spacing/Patterns tend to not be consistent at times but near not noticeable during gameplay.
As you may notice I didn't really put as much as I did for rhythm in this case because there is actually a lot to be considered around modding Spacing/Patterns namely to this main factor: Mapping Styles
Many mappers you know do all sort of mapping styles through many years which means different ways to emphasize spacing/patterns mapset to mapset.
What is an issue in this map may not be an issue within another mapset due to different ideology of mapping, you have to consider the mapper's preference in this case more than you would ever have to in rhythms.
All this is why modding these are actually more harder than what people think, since it requires an overall look thoroughly in the mapset, considering the overall mapper's choices within the mapset, and his style as a whole.
Whilst that may seem like an overload at first, it just comes down to analyzing the map as best as you can before deciding to make your suggestion as well as keep in mind; you can't just simply blindlessly add your own ideals into a mapset so easily.
Finding Spacing and Pattern issues/suggestions
Now considering what I said above, it is pretty easy to still find usual mistakes within pattern/spacing for even some new modders, but what really comes down to it is when we have to take into consideration of mapping style for instance, and that is when things gets tricky.
Upon looking at a difficulty, look through it overall first
I mention this within my rhythm section and I must repeat here since it is important to always look at a map overall. Especially when considering mapping styles into this as what looks like a mistake at first glance, could very well be an intentional part of the mapset as you look across it and see that it has been doing that same "mistake" consistently.
Of course with that being said what is intentional, doesn't mean the mapper is always right and likewise with the modder can't always be wrong.
After looking at the map difficulty overall, it may be hard at first especially when unfamiliar with the style at hand, but eventually you can have inconsistencies upon that too.
Patterns done before weren't here even if song structure is more or less the same, Spacing that the mapper kept using starts to seem out of place in it's own way, etc.
It always pays to have an open mind upon these things. While it doesn't hurt to point out your concerns by no means at all, it helps to see the mapper views on things more to potentially bring improvement on even your own views, as well as help the mapper more overall.