In which case either favorite or bookmark will do the trick, correct? Why worry whether you're clicking the "wrong" one?

Boost will also do it, but it has more side effects.

In real life, your friend tells you a moderately funny story that happened to him. You tell the friend, "nice story" (that's a like).

Another friend tells you a super funny story. You then go and tell other friends this same funny story. (that's a boost).

Different real life things, that are captured by digital tools.

What I have a problem with are quote tweets, which are like talking about someone in front of them, without including them in the conversation.

Because I don’t want to boost or add the toot to a perma-list, I just want to give the person that posted something I like some acknowledgement.