I'm with the majority: Users, no, but it could probably work (with caveats) for only the mods
and it may require extra work from you now and possibly later; or work (as intended) for just you and that would require less work overall.
But just curious...
>>> I could add the #done hashtag, instead of having to go to the website and editing the topic
- Construct reply as normally, but with #newhashtag also and email in. (?? OR, instead of the normal address, email the message to (non-published) group+addhashtag@groups.... possibly ??)
- If sender not an admin, treat as now, strip #newhashtag and post, done.
- If an admin, scan the subject hashtags to see if there is a new one (or ones if recursion was used for possibly adding more than one capability)
- If one found, use that and call the code that runs when a hashtag is manually added to a topic by the admin.
- Post the message now, and done.
Is something like this what you had in mind? It mimics an admin adding a hashtag so effect-wise, nothing changes, not any new disconnects or new side-effects; same thing if currently an admin did the topic hashtag addition by hand then turned around and send the message (with or without the new hashtag), or vice versa.