One annoyance that occurs is the presence of supposedly identical notes. This kind of situation is induced by user. It can be typically induced by people that import annotations from other app. I don't know if it is very common. In my case it occurred because I imported annotations from google keep and I had problem with synchronization with joplin. I ended up with two set of 5000 notes that are almost identical as some notes were modified and were not synchronized on all devices.
It has some similarities with the feature "Diff for conflict" (see Diff for conflicting notes) but it is not identical to it.
I think of it in the following situation: You search some notes and you identify two notes that looks similar and maybe identical. If the notes are big, it is quite annoying to check if they are identical and if there is a small difference, this would be very helpful to be able to see difference in order to do a manual or automated decision.
If notes are really identical, this could be recognized and user could choose which note to keep, for example.
If notes are only very similar, difference could be highlighted, user could edit one of them and copy missing part and keep only one if this is the case.