The idea of doing things AJAX is great, but I think I don't like this implementation.
I agree it isn't the best implementation.
It is hidden and regular users probably can't figure most of it out.
They wont need to for most. The preview functions will show automatically upon clicking preview. Users may not know it will pop up above the post/PM, it just will. Same goes for the poll option, and the predict a users name for PM.
Most of these will just happen when a user goes to use the feature as they normally would.
Double clicking doesn't work at all imo. It should be made more visible.
It literally didn't work on the test site for me, nor did a majority of the features, but I disagree, the double click work great and while something like that, and the lock topic may not be obvious, all that is needed is a quick tutorial from the admins in a mod room. I did this on my previous vBulletin forums.