I use the search function in threads periodically. It does seem to be functional.
However, I do agree with the OP...
I would prefer if both quoted text and replies gave two options:
Go to This Post
Go to First Unread Post
While one can use the thread search function to find specific posts, it would be easy enough to just provide the link.
Likewise with quoted text, I'm often more interested in finding the thread than the quote, so I'd prefer one-click access.
I find myself periodically searching my personal E-Mail for previous posts, and if I find one, then sometimes it next means hunting for it in the thread.