Sooo after most of the week puzzling with this, here is the (sorry) state of #mastodon bridges as I see it:
nostr:nprofile1qythwumn8ghj7un9d3shjtnswf5k6ctv9ehx2ap0qy2hwumn8ghj7un9d3shjtnyv9kh2uewd9hj7qgmwaehxw309ankcetpwdhkuct5daezuer9wchhyetvv9usz9nhwden5te0wfjkccte9ekk7um5wgh8qatz9uq3kamnwvaz7tmjv4kxz7fwda6xsetjwd682enx9ejx2a30qyt8wumn8ghj7un9d3shjtnyd968gmewwp6kytcqyqzxrl97e3xrxazrnyeddw83zf5uekmue9e667js4cmzmvf4536d6pxgyqp 's #mostr works great to surface content from Mastodon. However, actual 2-way communication with people over there seems to be functionally broken. The only people I've been able to successfully communicate with using Mostr are over on retro-gaiden.com (which BTW seems like a pretty cool place).
With every other server, even ones that ostensibly Federate with Mostr, notes don't show up on the remote instance and I get zero response. It's basically talking into a void.
Conversely, #momostr seems to actually work for 2-way comms. However, user and post discovery sucks. The same users and posts you'll see on Mostr will be almost impossible to find on Momostr by just using the search bar of most Nostr clients...
However, I've found a hack: If you use the `.well-known/nostr.json?name=` API endpoint of Momostr, and set the name to the Mastodon user `username_at_server.com` , the API will spit back the pubkey. Past this into your search bar, and poof, the user appears for you to follow.