Chrome 75.0.3770.143 on Android 8.0.0 on moto e5 play
When I try to perform an impossible action on a mobile SE site, there is no feedback. For example, if I lose network connection after loading a page and then tap "Show n more comments", it fails without notice. If I'm not logged in and tap "add a comment", nothing happens.
By contrast, on the desktop version I at least get a generic error: