I don't know. But I occasionally find files with names like foo(username's conflicted copy).db.

I do the Keepass thing too, and this has happened with it's files as well, but that doesn't seem to cause any problems.

Those aren't corrupted databases, it just can't merge so it leaves you to pick the version you want. Just pick one and keep using it, at most you'll lose some recent changes from the other computer.

I should have known not to use language imprecisely on HN. :)

To the layman, any situation that results in having Calibre show books which are not in fact there, or having books in the library which are not shown in Calibre, or having Calibre's check library function report that there are "invalid titles", "missing formats" etc., could be casually described as "corruption".

Sure, but the worst case is that you don't see books which are in your filesystem, and then all you need to do to fix that is click "Add books".