Almost forgot about this one but a support question raised the problem that the two separate permissions 'Can delete own posts' and 'Can edit own posts' are illogically linked under a specific scenario. Both permissions are independent and separate but if you enable both and set a global limit on post editing time, once the edit time expires it trumps the delete permission even with no reply. This is not the expected behavior as the two permissions can be set independent of each other. Edit is not the same as delete and should not be treated as such under any configuration, otherwise you would not need separate permissions in the first place.

Link to original topic:

http://www.phpbb.com/community/viewtopic.php?f=46&t=1642715#p9885065