I think it would be reasonable to say that threads which were imported from before these forums existed, should not be bumped.

However, I would generally prefer not to lock them, for a technical reason.

If an old post has relevance to a new discussion, it can be helpful and productive to quote the relevant part of the old post in the new thread. In order to quote a post, one selects the portion they wish to quote, and clicks the “quote” button. This begins a reply in the same thread which contains the quoted material. One then copies the quote out of there, and pastes it into the new thread.

However, locked posts cannot be replied to, hence they cannot easily be quoted. In general, if the portion to be quoted contains non-trivial formatting, one would need to look at the raw text of that post—which there is no button to view, you have to know the [secret URL incantation](https://forums.swift.org/raw/64431/2)—and construct the quote manually with the proper link and attribution.

Thus, when old posts are locked, it becomes much more difficult to quote parts of them into new discussions.

Indeed, the same issue arises when proposal review threads are locked after acceptance or rejection. It becomes difficult to quote those discussions in the future.