Mastodon: Domain blocks improvements on the user side

[eramdam]

I've seen this feedback floating around on the fediverse recently and it's justified IMO:

While hiding a specific domain is fairly easy in the UI, there are no (or at least no easy way) to:

• know what domain you previously muted
• unmute said domains. Currently the only way to un-hide a domain is to go on a user's profile who is on the domain you've hidden and click Unhide <domain>

I feel like domain hiding is a very powerful feature for users but the lack of proper UI related to it seems confusing at best and dangerous at worst.

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• [x] I searched or browsed the repo’s other issues to ensure this is not a duplicate.
• [x] This bug happens on a tagged release and not on master (If you're a user, don't worry about this).

[npdoty]

Blocked domains are also currently not included in the export/import of block lists; if they were, I could take my list of instances I don't like between different instances.