When I opened
the question was still not answered by other users. I left that page open in a tab of my browser and a few minutes later I replied to the user. However, in the mean time, other user had already posted a reply. If I knew that, I would have posted something slightly different in my reply. In a situation like this, Flow should notify me that there are new comments in the page I'm replying to
LQT checks for updates once per minute and shows "This thread has new posts" whenever that is the case.