@dtBy I'm not sure where that onboarding info is? It would be great; I had a difficult time (most of the pubs listed on the pubs page not working, etc)

~dtBy if they can't see that message, then the right thing to link them to is my feed ID, not the message ID.
The message ID does not encode any information about who posted it, so with only that ID, the ssb client cannot easily figure which feed it needs to replicate to receive that message.
Once the feed is replicated (by following, or in patchwork as a one-off replication by opening the feed's page) then the message should show up in the thread. Might need a Ctrl-R refresh in some cases, or at least navigating to some other page in the meantime and then back to the thread with the previously-missing message.