I am sure that having a track record is helpful in terms of perhaps maintaining a thread.. but what is the idea of pinning?
A new thread might refer to the old thread (and linking it) and then perhaps summarizing aspects of the old thread (including perhaps updating some information). What would the pinning do? close the old thread and then link to the new one?
Not sure I understand the question so pardon me if this sounds patronizing... pinning is what makes the thread appear at the top of the board. That's basically the only reason to have this discussion at all, otherwise anyone can just create a thread and have at it, but they would not have the visibility that this thread has.
As for how the content is transferred, there are obviously options - linking, summarizing, etc. I think quoting the non-obsolete parts would work best - that way authorship is preserved and the contents is still in one place without having to click too many links. Rewritten parts can have reference links to the old stuff if needed.
Mucking around with ownership doesn't make much sense IMO, nor does keeping outdated info at the top of the board.