Share in the thread header creates a public link. Anyone who has that link can read the conversation without signing in.
What the link publishes
The title.
Every completed message, yours and Marl's.
The web sources Marl cited.
Messages you send later. The page keeps following the conversation.
What it does not publish: your attached files, and anything about your account.
The page asks search engines not to index it. That is a request, not a guarantee — treat the link as public once it leaves your hands.
Stopping the share
Stop sharing disables the link at once for everyone who has it. Sharing the same conversation again later creates a new link; the old one stays disabled. If the page reports that it could not stop the share, assume the link still works.
Organisation conversations
Share links are for personal conversations only.
If the link does not work for someone
A shared page that reports itself unavailable was disabled by its owner, or the link was mistyped. There is no way to re-enable an old link — share again and send the new one.
Quavern help reference: sharing-a-marl-conversation/en