No top button when viewing a comment - only parent. No way to undo/reverse a vote. Comment reply/edit is on another page instead of inline like reddit. No comment reply notification in the toolbar.
I second that. Much needed.
Undoing a vote, even if it is useful, would add clutter to the UI. Because I always enjoy the sparseness, but would rarely want to undo a vote, I think the site is better off without the feature.
No, it would just leave the arrows in place except highlighted when "voted". You could then click it again to unvote, or click the opposite arrow to reverse vote. Just like Reddit.
I'm not saying I want unvoting, as I don't really care, but I don't think it clutters the interface in any meaningful way. (Though it does make the pair of arrows multi-state, which could be confusing for some users. Doesn't seem to bother redditors though.)
Adding undo wouldn't add clutter, just see how reddit does it.
Also the text (as I'm typing this) in the form field is too lightly colored and the text area is too small for me.
My biggest nitpick is reading the grayed out font on visited links, submission text, and a few other places. My brain wants to skip over grayed out text so much that it requires an almost conscious effort.