Basically any change you make it insta-reverted by some bot or over-zealous power-crazed editor.
I think some editors decide that they "own" certain pages or group of pages and install themselves as some sort of authority/gate keeper/moderator. If your edit does not please them, it's gone. Instantly. You only get to edit the pages if you are in the editor's cabal of friends.
If you don't have an account, or you do have an account but perhaps have only made a handful of edits, you are instantly distrusted and assumed to be malicious.
Of course, you can never prove that you are not malicious, because there is the default stance of immediate-distrust for anyone, so your edits are constantly undone and you never get to build up enough credibility to appease the editors who control who gets to edit "their" articles.
I gave up years ago after a small edit-war with someone who kept reverting changes about a UK politician who was in national news at the time. No amount of references or citations from e.g. the BBC or the Guardian was good enough as I guess the verifiable truth didn't fit with their view of what this page should selectively say about that person, and so they banned my IP as a "vandal". I gave up (but got a new IP after redialing so it was pointless)