If I
- open any post on any Stack Exchange site in mobile version (Chrome 63 on Android)
- then click "add a comment"
- then type
@ - then type first letter of user name which already commented to this post
Then no username autocomplete happens.
Here is gif where I try to autocomplete @Mureinik in this post:
In desktop Chrome autocomplete works as expected (that is after typing @ and first letter of username, popup with username appears):
Sorry if this question is duplicate.
I don't know exactly why this is not a bug (@iDebug says so), so I put both bug and feature-request labels.

