Muting & Blocking with author urls

The spec mentions "hiding all posts with the muted user's profile URL", but what happens if the server cannot parse a url for the author?

I suppose it would be very difficult to block an author if they do not have a url associated with them.

It would either be worth documenting what to do if there is no author url, or provide another method for blocking the author.

Read the Microsub specification section describing muting and blocking by the author's profile URL. Determine the required behavior when an author URL cannot be parsed, then document that behavior or define an alternative blocking method. Done means the specification no longer leaves this case ambiguous.

Written by the indexing model from the issue text.