I never interpreted Your Mouth as about the break-up per se, just a reflection of the stuff he was going thru at the time, Mother City's about going to New York at the time, not about the break-up, My friend the enemy's about drugs not the break-up itself, etc, etc. I may well be wrong, but I always thought it was just about some annoying twat who says annoying/hurtful shit that one of these days is gonna get themself a slap.
I can't say it's a favourite of mine, but I don't think it's shit either.