I guess I’m a bit confused here. Are you strictly talking about visual inconsistency or are there usability issues?
We use icons in different ways because they provide different levels of meaning in different contexts.
We’re intentionally creating two mental models here. “Closed” or “Pinned” isn’t descriptive of what the topic is about, so it’s a status and not a tag. Are there benefits to statuses as tags outside of the desire to not use icons for statuses?
You tell me. Did you click on an icon and become confused about its action or lack of action? E.G., Did you click on a lock in a topic title expecting it to do something? (not trying to be obtuse here, I’m really just not understanding what problem is in need of solving).