Yeah, sounds like a combination of things: a11y allows introspection of the widgets, and perhaps received messages are rendered by an editable widget that's "em

Yeah, sounds like a combination of things: a11y allows introspection of the widgets, and perhaps received messages are rendered by an editable widget that's "emulated" to be read-only (ie most events caught to make it non-editable, but a11y goes direct to the properties). Since you can't reproduce it, sounds like an inconsistency in startup too. Perhaps worth trying to kill the Messages app and restart it with a11y reenabled? You should probably report the bug anyway, it might be an easy and obvious fix for someone with access to the source code, yet hard to figure out a reproducible test case for an outsider.