When comments are moved to chat, pings in the chat room do not notify anyone until the pinged person visits the new chat room. This often instantly kills the discussion entirely, simply because the participants are unaware that there are new comments to respond to.
I requested changing this a few months back, but it might be simpler to notify all authors of the moved comments about the move. An
@ ping for each of them in the "moved to chat" comment should work, though doing it in one comment would require exempting this system-generated comment from the prohibition on pinging multiple people.