@Gargron "quote posts" should be a type of reply. ie: quoting a post doesn't escape the thread, it just boosts the thread in your own TL at the same time as replying.

That's my only objection to a "quote" feature: it encourages drive-by comments about another thread, rather than promoting discussion within the original.

example UI: a tickbox when writing a reply which says "also boost", and on your TL it boosts the OP while also making your reply visible. Call it a boost-reply.