What this server publishes about itself, on /about and through the instance APIs every Mastodon client reads. Saved here, applied immediately, no restart.
[instance] section of the config file. Clearing a field makes it fall back to the config file again, except the rules, which stay whatever this form last saved, so clearing them publishes none.[instance] section of the config file, and nothing has been saved here yet. Saving copies them into the database, after which this form wins for every field it holds a value for and the config file is only the fallback. The rules become all-or-nothing: whatever is saved here from then on is what gets published, empty included.