What is wrong with a phone call (preferably scheduled) to work out such details? It seems to work pretty well for me with my remote job. I prefer more complex solutions to be worked out via a wiki-like editable document that everyone can share and discuss, but for trivial things, a phone call works well.

You are right that many more things could be done without so much collaboration with better practices. I think code reviews can help maintain a sufficient spread of knowledge across the team.