@Pineywoozle @lorenzlm @jeffjarvis @vowe A QT, enables call and response and INVITES the response through the very mechanisms that many of you describe. Insofar as the QT actually pulls the other user into the conversation or adds something new to it, the QT invites a participatory exchange that the screenshot + hashtag does not.
This is how the QT enables the call and response I've been talking about in a ways that your proposal does not, and which mastodon was not designed for.