Of what use might it be having a mobile interface@OP, for there to be a need for this modification, it implies there is a pressing disturbance that necessitates this modification but so far, I haven't seen any. I use mobile quite often and I'm not restricted to any feature or don't see a future that is unique to PC that is lacking on mobile except the restrictions that applies based on rank which goes for the two media.
The forum is pretty much stable for me, you zoom in and out if you have problem with viewing the font else, the mobile interface is very much stable me or perhaps it's just what I'm used to. Again, should the interface be too small for you, simply rotate (change your screen setting) to landscape while accessing the forum and you just might have a desired view.
I wouldn't say its stable but more like unoptimized, because if you were to visit other non-responsive sites, they would be rendered similarly to Bitcointalk's.
Imagine trying to amend/ trim a quote just to reply, it's
hard. Since we can't resize the text field unlike on the desktop.