Just noticed this: (source question)
After quick check on other question old and heavily downvoted and not closed, I can indeed cast a vote and it's recorded.
I see the link on all questions including upvoted questions here on Meta.
and Stack Overflow too.
I double checked; did not get any diamond.
Not sure it's related and don't remember if it was showing delete votes before, but the "Delete and Undelete votes" tab in 10K tools is empty.