If the mirrors are creating 250k new mirror accounts per day, and if one fediverser instance can convert 0.1% of these per day, it’s 250 new users who “don’t care”. In one week, these ~1500 converted users will be in conversation on both networks, which will increase the number of non-bots in mirrored threads and be enough to stop the “ghost town” feeling.
If that’s not a purely hypothetical argument then I don’t know what is. Your conversion numbers are taken from thin air, as is the claim that those numbers will prevent or revert the ghost town feeling. You completely ignore users signing up or going back to Reddit, you assume that everyone migrating will be ok with sharing their stuff back to Reddit, and so on. The fact of the matter is that you’ll be creating a read-only copy of Reddit at the beginning, and there is no telling if that will ever convert back to a real community. But in the meantime you’ll have spammed a lot of communities with tons of bot content.
I mean, try it on a few communities that agree to this and see how it works out, but don’t let something like this loose on Lemmy as a whole.
The worst that Reddit can do is to revoke the keys by claiming violation of the terms of service.
I’m more concerned with the personal rights of Reddit users than whatever Reddit as a company would do, although violating their ToS on a big scale might have consequences as well. IANAL so idk what the right answer is here, but an approach like “it’s fine as long as they don’t sue me” is pretty reckless imo. Maybe take the rights of the people you affect into account before flipping the switch. E.g. what would you think about someone creating a bot account of you on FB and posting all your stuff there?