I reported a bug in the beta mobile code, using Bugzilla, in which the "speech balloons" button on user pages misgenerated the name of the talk page it was supposed to link to. That bug was put into Phabricator T54165 (https://phabricator.wikimedia.org/T54165#562123), by @Florian I think. It has been fixed (code review https://gerrit.wikimedia.org/r/#/c/173541/) and the task properly closed.
But in testing the fix I found a new problem, or at least one I hadn't noticed before. The beta mobile version shows a speech balloons button on talk pages as well! This happens on article talk pages as well as user talk pages; I haven't checked other types. The button doesn't actually do anything, which is good because talk pages don't have meta-talk pages. But it's a really bad idea to have a do-nothing button that looks just like the corresponding real button on other pages.