Have not seen this symbol before, maybe it has something to do with wifi or internet connection?
Even if it does why is it showing up in a text editor while you write posts.
Looks like the Volume is muted on your phone?
Nope. Has no relation whatsoever.
One more thing I noticed, initially no symbols show up but a few seconds later they do. I use Firefox on Android so if it is related to that... Is it by any chance a sort of a keylogger?