I like this idea though I think if like your mock it might make the header a bit too cramped and a bit too noisy. But a good idea just the same.
Our use case would be to help with “hijacking”. There have been times when a member will join in a discussion with a kind of “me too” post, and then encouraged, bring the discussion off-topic from the OP with an “also” post. Sometimes a little meandering is ok, other times it can leave the OP out of the discussion.
I guess the usefulness of having the OP identity visible would be mostly as a clue that a topic should be split when we see a “mid-topic OP”.
I’m wondering if it might be better / easier to give the OP’s avatar the “halo” similar to topic lists.