For example a political post in s/nopoliticshere can be moved to s/politics by the mod of s/nopoliticshere.
This accomplishes several crucial things:
1) Prevents censorship (and drama) by not removing the content. The same thread exists, just in a different sub and still shows in s/all.
2) Grows niche subs. Maybe nobody goes to s/politicalmemes but they will if they like the content that gets moved there from s/funny.
3) Keeps content relevant to the sub in two ways - subs get relevant content imported from other subs, irrelevant content gets removed from the other sub.
Discussing this in IRC the main concern was abuse. A mod can dump a bunch of posts into other subs. A potential safeguard would be for mods to disallow transferred content from other subs. When another mod tries to transfer content there they get an error and have to choose a different sub. And of course the receiving sub can just transfer the thread again if they wish if they allow transferred content.
There still has to be a full deletion option for illegal content, but I think those instances are few and can be handled through an admin reporting system.
I think this is a good feature, to just be able to turn it off, but perhaps accepting transfers would also be a helpful feature.
I do think this could cause problems though to be honest, ones that we can't even foresee. People are going to be pissed if one of their posts is moved from a default to a non default, because it will get less exposure, for example.