Thanks Michael.
Often, I find myself "choosing" which reply button to use. It is at least a UI problem, with some similarity to Ben's post (https://openacs.org/forums/message-view?message_id=247645).
"Reply to conversation" and "Side note" would do for me, where the Alt-tekst of "Side note" would be "New thread, but relevant to conversation" and the reply would not be visible at the standard thread level.
Having to click to another thread level to see a "Side note" would feel like listening (on the side) to what two individuals are saying to each other in a conversation.
"Side notes" can easily become new threads... which is probably not what you want from a developers point of view, but this is what happens in real conversations. So maybe "Side note" should really be a new thread (with a parent), but with a clear new title.
