Who controls glibc?

Fixing small things should only require small reasons. If you have to think very carefully for days, consult dozens of people, do a cost-benefit analysis and write up an extensive rationale document every time you clean up a bit of code or a bit of documentation, it clearly won't be worth the effort. Then the project will collapse under the combined weight of a million tiny problems that nobody bothered fixing.

Efficiently fixing trivial issues seems like a requirement for sustainable software development, not a sign of its demise. (And it sounds like this patch was being handled efficiently until Stallman got involved). Sometimes projects will explicitly talk about paper cuts (minor usability bugs that are individually unimportant, but a user who encounters dozens of them will be strongly put off) and technical debt (problems that weren't worth fixing in the short term, but their cost will accumulate until they seriously impede development) because they're aware they need to deal with those minor issues - it's tempting to ignore them and focus on the highest-priority issues instead, but it's important for the project's long-term health to work on the little things too.

(Besides, in this specific case it's easy to find people like https://stackoverflow.com/questions/48445031/why-would-it... who seem genuinely confused by the statement and wasted an appreciable amount of time trying to understand it, so it's not a hypothetical problem.)

You're right, removing it won't (at least in the short term and likely not in the long term) drastically change anything for anyone. You've been saying this is a waste of time while other bugs are still festering, but consider for a second how much time it actually took to make this change happen. Someone saw the "joke", deleted it, committed it. What is that like 30 seconds of work? This isn't a bug that needed hours of time to discover and fix technically or socially, and the quick change could have some benefits for the project in the form of more contributors.

The real issue (and time waster) was when RMS came in and exerted authority he no longer deserves to have (I understand he is an ideological lead and not someone doing technical work, correct me if I'm wrong) thus creating an argument that anyone watching from the outside will see RMS as an overstepping grossly immature leader. Again, not for the joke but because of the authority he is trying to exercise over something so minuscule. If anything deserves "RIP for glibc" it's his behavior, not the 30 seconds of work it took to remove a dumb joke. And if jokes like that aren't turning people away, it will be seeing arguments like his unfold that will make potential contributors go "oooh...maybe I don't want to get into the middle of that culture..."

And all of that you could ultimately blame on someone making minor changes that don't need to happen, fine whatever maybe you're right. But the trigger for this argument and his excessive use of authority could have been more technical and we'd have the same argument at hand, it's probably happened before. This specific instance is easy to separate the technical from the not and so it ends up being reported on.