I get this. Have done for at least 18 months, maybe 2 years.
My info:
- only happens on one of multiple forums
- happens in DiscourseHub app mostly
- also happens in macOS desktop Safari
- I never open the same page in multiple tabs, never mind editing the same post in multiple tabs (in fact, it’s not possible to do that in the DiscourseHub app)
- before the warning message I see a warning triangle in the bottom right under the composer
- I first reported this 18 months ago to the admin of the forum in question
Also reported recently at the forum in question: "Draft is being edited in another window" - #6 by matt - Playdate Developer Forum
I believe that forum is the only self-hosted forum out of all the Discourse I regularly use.