I hope more #ActivityPub implementations start properly handling JSON-LD documents in various forms, rather than using ad-hoc approaches like only allowing specific fields to accept both arrays and scalar values.

Or, just use a proper JSON-LD processor altogether. Of course, there would be a performance penalty. The #ActivityPub spec explicitly allows as:Public or bare Public for public addressing in to/cc, etc., but surprisingly many implementations don't handle this. All of this would actually be solved by using a JSON-LD processor.