I use quotes all the time because I very often read a note and it makes me think of something that I may think is note-worthy.
But I may not feel the need to reply to the original note, maybe because it's not directly related to the content of the note, but most often because I simply do not intend to allude directly to the author, or even less to engage in a conversation with him/her. If and when I do feel the need or the wish to engage someone directly, I use the proper method, that is, a reply.
Both people who quote and people who are quoted should understand this difference.
