Who controls glibc?

Systems that have a compulsory voting system typically have abstention as an explicit option, which allows for the kind of protest you mentioned: it is compulsory to cast a vote, but you may cast a vote for "none of the above".

This is used on a national elections level in Australia, where voting is compulsory. There isn't actually a "none of the above" box but it's perfectly legal to turn up to the polling station and hand in a ruined ballot card, which is the defacto way of abstaining.

It's indeed a bit presumptuous to lump "I don't care" with "I strongly disagree with all options" in the absence of a voting system that doesn't distinguish between those options. However, on a software project mailing list, it's not the case that there are a fixed number of options to vote for---if somebody disagrees with all possible proposals that have already been suggested, they're free to introduce an alternative suggestion. So in that context it does seem reasonable to read an abstention as "I don't care about this issue" or "I agree with whatever the current consensus is".