More for other mods to be aware that it’s not going to work quite as smoothly as they might hope. But yeah adding that to the bot replies makes a lot of sense, good thinking!
I’m wondering, is it all or nothing in terms of which posts get tagged? For example I mod !knitting and most of our posts are someone showing off a project, which is easy to comment on from Mastodon (I’ve been boosting and replying to stuff manually to draw attention there as you described in your OP). But then we also have things like Work-In-Progress Wednesday, where multiple people are posting images of their WIPs to one thread. This doesn’t work so well with Mastodon because images don’t federate (in either direction) with the exception of the first image attached to the main post, so there’s no point sharing it there.
Not to give you more work but maybe it’s an idea to have an opt-out keyword that can be included in a post, and the bot will know to ignore that one?
Again, really is great work, you’re always contributing useful stuff to the Fediverse and I for one really appreciate it so please take these rambling thoughts in the constructive manner they’re intended, they are definitely not complaints 😄