Even if i do reply to my own post it adds a mention :D
I have just noticed another problem with that on mobile. It adds a mention automatically and it works like a link. If i try then to press in the field to type a comment on my tablet it just works like i have clicked on that name and editing box goes away. I can't type replies to people on my tablet anymore because of that (Huawei, Android 5).
Fortunately on my Pixel with Android 9 it for some reason not loading editing tools and don't add mentions (looks just like Quick reply), so i'm still able to discuss things on my phone (because of another bug).
