Voting buttons were removed from user pages to make mass-downvoting marginally harder, except for for users with sufficiently high karma, looking at users with sufficiently low upvote percentage.
But it also prevents me from voting up or down from the list of my own posts (with the posts I'm responding to above), or from my inbox.
In this case, it prevented me from upvoting someone (presumably with high enough karma) who I was in a short thread with. Just inconvenient to have to chase the permalink.
A while back (a couple years?) votes (or at least downvotes) were disabled on per-user "overview", "comments", and "submitted" pages, to make it harder to karmassassinate people. Sometimes there's a bug where you still see the vote buttons but if I remember correctly they don't work.
(You can still vote on a comment after following its permalink.)
OK. (Although -- have you refreshed the page or gone to the permalink to see if the vote is still there? I kind of remember that the vote button changed color but didn't actually record the vote.)
Anyway, I looked it up and in 2011 Eliezer said, "Voting buttons have now been removed from user profile pages."
I'm just saying that it is intentional that you can't vote on the comments on someone's profile page. (I found the relevant entry in the issue tracker.)
I was about to say that if sometimes the buttons do appear then it's a bug, but it turns out that this behavior has been changed:
Users with sufficient karma can downvote on the userpages of people with less than a certain percentage upvotes.
It was intended as a META tag for subject type, to distinguish it as being about the functioning of the LIST (probably not the best choice) instead of an actual topic.
As in "list of comments"? I don't think people use that phrase very often.
Also, I think it's too specific and META would have been better.
Just showing my age, I guess.
I think of it as a mailing list, and in particular, was copying the meta tagging usage of the old Extropians list. Probably lots of things would have been better, the first that come to mind are "Forum" or "Forum Software".
META pinged a few neurons, but seemed wrong, as it was used more to apply to comments about other comments or threads, and often moderation issues, but not about the software.
What's up with that?
In a discussion thread, I can karma vote on anyone.
But if I select a person to see all their posts, for some people, karma is disabled while looking at them, and for others, it's not disabled. Same thing if I look at their posts under the list of all my posts.