Previously, historically locked questions (and the answers) had their voting buttons hidden. The faq says:
In addition to the post notice being prominently displayed, posts which are historically locked are "frozen in time": they cannot be voted on, flagged, answered, edited or commented (though they can be favorited, and ♦ moderators can edit and comment; moderator edits to historically locked posts do not bump the posts). The visual appearance of the entire post is altered by removing the voting arrows from the question and all answers.
Now, somehow the voting buttons are shown on historically locked posts:
- The new top bar is out on meta. Consider it a beta
- "Thinking in AngularJS" if I have a jQuery background?
This is probably related to the recent changes, especially as the buttons are hidden in the mobile view ("mobile" link in the footer) as Solomon Ucko noted in the comments.