@ta180m I've been looking at the spec, I don't see much about this. This would be acceptable behaviour for unsupported object types, but this could easily go wrong. I am not a fan of the idea, at all. For example, PeerTube creates a "View" activity for each time someone watches a video. If someone decided to refer to those in an `object`/`inReplyTo`/etc field on their activities, this would be a nightmare.

Type arrays can and should be supported, in my opinion. JSON-LD also has what's necessary for extending types, as well. Issues then come as to how to represent such types (should Repositories really be represented as accounts? how would one star an account from current Mastodon/etc? should Issues be represented as posts? should people be able to hellthread a repo's issues from a social network? emoji reacts?)