Yes, I considered this objection, thank you for bringing it up. Upon consideration, it seems to me that "compulsory attendance of the voting booth", while probably not literally inspired by actual sadism, is perverse to the point of being indistinguishable from sadism.
If a country gets "inadequate voting outcomes" (what does that mean, exactly?) from volunteer-only voting, compelling people to vote seems to be exactly the wrong solution for many reasons. (Voting is a "commons problem" to the extent that it is a problem — but it's not clear to me that "few eligible voters are actually voting" is, in fact, a problem.)
However, the more relevant-to-the-conversation response is that "society's" interests in this case are far too diffuse and theoretical to serve as any kind of relevant analogue to the case of "one very specific person (i.e. Bob) doesn't want unpleasant experiences inflicted upon him". That's what makes it a poor analogy.
Non-compulsory voting has the disadvantage that certain people will refrain from voting just because of the inconvenience of going to the voting booth and others won't, which may bias the result of the election if the extent to which voting would be inconvenient correlates with political positions for whatever reasons.
r/Fitness does a weekly "Moronic Monday", a judgment-free thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. I thought this seemed like a useful thing to have here - after all, the concepts discussed on LessWrong are probably at least a little harder to grasp than those of weightlifting. Plus, I have a few stupid questions of my own, so it doesn't seem unreasonable that other people might as well.