Heh. This is funny. Explains a bit. Quality != Consistency != Efficiency
Capital letters in usernames

There's a likely or probably excuse behind these things, but, to anybody doing software development: The reason probably makes some sense, but the explanation probably exposes any number of potential issues.
Pointedly: The lack of consistency means pulling information from different sources via different methods without consistency in terms of how things are pulled together and reported. And any time you have this sort of situation, you probably have any number of other problems or issues, either front-of-house (exposed, or likely to be exploited) or back-end (worst-case-scenario).
Is there any reason to provide names of players in the list of "fair play removals" at the match endpoint keeping its capitalization? Or is it just an oversight? In list of players spelling of each username is lowercase. Maybe, it would be better to have them in the same style?
Example: https://api.chess.com/pub/match/862300
For sure, API (as well as website itself) works well with any capitalization (e.g. https://api.chess.com/pub/player/sebachEVA ), but be aware doing a comparison of strings in your code. You should explicitly convert names to lowercase.