The question in question:
1) My original question was "edited", in ways that add nothing meaningful (slight changes in words, but not meaning or fixes in grammar).
2) I edited the answer I planned on accepting, because I found additional relevant information, which completed the answer:
Note that this edit was accepted. This is also very much in line with accepted etiquette for when answers should be edited: Why can any user edit any other user's question or answer?, and something I am used to doing on other Stack Exchanges.
However, this edit of mine was rolled-back (to a state where I would not fully accept the answer any more), and the following comment was left by the editor responsible:
Except that the edit I made was not much of an alternative, it simply notes that the source code for Unity's UI Engine is officially available. The editor made further edits to the answer which were trivial comma additions.
My immediate reaction was to simply delete my gamedev.stackexchange account and move on, rather than deal with this annoyance, but I have decided to take out the time to put together something more comprehensive to the meta community, in case I am in the wrong. Please advise.