There are “announcement” communities where all posts are treated as announcements. This all-or-nothing blunt choice at the time of community creation could be more flexible. In principle, a community founder should have four choices:

• all posts are announcements (only mods can post)
• all posts are discussions
• (new) all posts are announcements (anyone can post)
• (new) authors choose at posting time whether their post is an announcement or a discussion

This would be particularly useful if an author cross-posts to multiple communities but prefers not to split the discussion. In which case the carbon copies could use the announcement option (or vice versa).

There is a side-effect here with pros and cons. This capability could be used for good by forcing a conversation to happen outside of a walled garden. E.g. you post to a small free-world instance then crosspost an “announcement” in a walled garden like sh.itjust.works, then the whole discussion takes place in the more socially responsible venue with open access. OTOH, the same capability in reverse could also be used detrimentally, e.g. by forcing a discussion onto the big centralized platforms.

update

Perhaps the community creator should get a more granular specification. E.g. a community creator might want:

Original posts → author’s choice

Cross-posts coming from [sh.itjust.works,lemmy.world] → discussions only

Cross-posts coming from [*] → author’s choice