It's all in the @propolis.eng account, edits do edit the post. No new rewardables.

I guess the hard part would be knowing how much of the contributions are vetted and how much effort was put behind it, I.e. someone didn't just copy a contribution already on wiki and pasted it on your app for some post rewards by an unknowing curator.

Absolutely. Not just copies, but also structuring, formatting and sourcing. A good wiki post is a post that doesn't need edits by others, but that's not something curators on hive look for. Giving hive rewards to authors wouldn't lead to a high quality wiki, but a few minimum effort posts about topics that would have a probability of attracting a high value vote.