The problem I’ve faced is that even if the subreddit wants to build up a community here, users eventually stop posting if no one from their original community is seeing the content.
They were not opt-in (and I’m firmly in the camp that believes that “opt-in” bridges are a bad idea), but that was the second most important pain point that I wanted to solve with the alien.top bots (behind it being a tool to help one-click migration).
The tool should check if the OP of the post included a flag (…) either in the title, post body, or as a top comment.
This feels like it can become a brittle solution and can get way too complicated fast. My plan for fediverser now is to let people create bridges by authenticating with their Lemmy and Reddit account, and then specify what type of bridge. E.g, users could choose if want their responses in Lemmy to become a response on Reddit, or just to send a PM to the OP indicating the Lemmy link.
In any case, I’d personally favor any approach which establishes that the net flow of content is out of Reddit, not in. If we keep mirroring the content from here to Lemmy, the people there will have even less incentive to leave, but if we use the intolerant minority strategy we might end up forcing the majority to migrate as well.