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.
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.