The forum software is Discourse, not Discord, which is a common enough mistake due to the similarity of the words!
This isn't a new issue, here's a screenshot of my old report from 1.5 years ago.
And here's it happening as I typed this post. 
The only other thing to add is that when I'm typing i do a lot of editing (moving the cursor position and changing what has already been typed) due to mistakes and clarifying my wording, and whatever is happening whilst I'm editing seems to trigger this. If I just type and don't edit, it doesn't seem to happen. Maybe it's related to length of time typing.
And I'm wondering if the warning triangle indicates a connectivity issue, and the warning message is a false positive not really indicating the real problem?
Finally, I don't have this issue on 4 other Discourse forums I use. Which is odd.