Yes, it does.
And it is not at all limited to Android chat apps, if have seen in in Android text editors, when typing in text fields of web-pages in Firefox etc. It is reported and discussed a few times (= in a few threads) at TJC, but I cannot remember any sailor ever replying or acknowledging this issue. Still, Jolla has addressed this issue multiple times (silently, as so often, observable by changes in details of this behaviour) and reduced its severity / impact much; at times it was literally impossible to type a few words in most Android apps, if you ever needed to use <Backspace> (i.e., correct something you typed).
Observations
My preliminary, abstract assessment is, that it always (i.e., all these years > 7) takes a new word (i.e., introduced / prefixed by a space character), then a delete operation (regardless, if by oneself hitting <Backspace> multiple times, or automatised, see example in OP above: the string :duck is deleted and an emoji inserted), followed by typing <any key>: Then the deleted string is inserted again.
It appears that Jolla has employed workarounds, which let this happen less often, but never found the root cause of this issue.
Mind that there are different kinds of text fields, I only remember this happening in free text fields. OTOH, I have never tried to reproduce this systematically outside of free text fields, e.g., in a password entry field etc.
P.S.: @thigg, you might adapt the title of this thread to the fact that this is about text strings (“commands” is a bit misleading, even for your emoji example) and potentially affects all Android apps. Plus that this is related to Alien Dalvik (“Android app support by Jolla” is its new marketing name; I never heard a Waydroid user complaining about this issue).