I don't know if there's any way to actively hide a thread from appearing in the stream.
"neither unfollow nor delete kept them from coming back when new replies showed up."
The annoying bit is that I usually try this because it is the continuing conversation I don't want to see anymore.
How to stop notices in the Network stream widget than?
Leave away the https://.email@example.com seems to work for me.
or just fallback to default more gracefully?
The general rule is that if a custom theme on a different site is your default theme and it isn't available on the clone, you'll fall back to redbasic. If it does something different, please let us know. Also if you've got a better idea...
Hardcoding themes if it's theoretically possible to remove them and replace them entirely with something else should be avoided IMHO.
For example, if you have a knowledge base or recipes on your hub, the redbasic theme will not have any navigation to those pages. The user will be unable to access the rest of the website if you default to redbasic.
If you use the existing infrastructure to extend Hubzilla (addons, apps, widgets) navigating those places should not be a problem.
the site will not fallback to redbasic if the the default theme, as set by the admin, is available.
If what you are saying is supposed to be true, there is some sort of bug.
There are themes besides redbasic? Not being sarcastic--my install didn't have any others.