the example seems confusing semantically; right now, it looks like an Authorization activity performed by bob and attributed to both alice and bob.
from a data modeling perspective i don’t particularly have any opposition to a base Authorization class that can be subclassed as LikeAuthorization, ShareAuthorization, ReplyAuthorization, QuoteAuthorization, and so on as needed.
i think it’s also possible to have a more generic “link approval” that can be an attribute of a generic web link? so take the approvedBy and make it not only a property of as:Link but also an attribute of Link headers or a/link HTML nodes? RFC 8288 - Web Linking – although it’s unclear when something is a string and when something is a URI