Add separate "Default visibility for replies" preference

[runevision]

Problem: I've seen suggested many times that it's "good form" on Mastodon to set replies to have unlisted visibility instead of public. One can agree or disagree with this, but for those who subscribe to this logic, it would be nice if replies could be unlisted by default so one doesn't have to set it every time (or conversely, set original posts to public every time).

I'd like: An additional preference to the "Default visibility" preference called "Default visibility for replies".

By default it should probably use the same setting as for original posts. This could be done in a few ways.

Approach A: The "Default visibility for replies" preference could have the options:

• Same as for original posts
• Public
• Unlisted
• Followers-only

Approach B: A toggle "Same default visibility for replies" could be shown, and below that a preference "Default visibility for replies" with the options:

• Public
• Unlisted
• Followers-only

Potentially the option below would only have to be shown if "Same default visibility for replies" is disabled, though opinions differ on such practice. Alternatively it would be grayed out (inactive) when "Same default visibility for replies" is enabled and show the same chosen options as for original posts.