The yellow/orange envelope notifies you that someone has responded to your comment in a thread. Those “private messages” you are seeing aren’t really private messages—just a feed of others’ replies to you.
But I can see how that would be confusing, since that same icon also lights up when someone sends you a PM.
(I trust someone more awake that I am can make this anecdote into a nice illustration for why we have low confidence in the reliability of eye-witness testimony about aliens.)
The yellow/orange envelope notifies you that someone has responded to your comment in a thread. Those “private messages” you are seeing aren’t really private messages—just a feed of others’ replies to you.
But I can see how that would be confusing, since that same icon also lights up when someone sends you a PM.
(I trust someone more awake that I am can make this anecdote into a nice illustration for why we have low confidence in the reliability of eye-witness testimony about aliens.)