In reply to Robert Durran:
> Maybe. But is that a good or a bad thing? Am I placing my right foot clumsily to cause the wear or more or precisely hard against the back of the hold? ie is it good or poor technique?
If it is from placing the feet, then bad technique (lack of precission).
But as you say that this happens mostly on your indoor climbing shoe, I think it is the case of dragging, smearing on intermediate wall on long moves... in which case (at least the intermediate smearing) is considered and advanced tactic/skill.
Try to assest if you do a lot of high steps on the left foot with the right (stronger) arm on the hold. For these, quite often people try to get additional momentum by smearing the right foot on the wall with intermediate increments (good technique, but on coarse wall, will lead to excess wear on the inner tip of the big toe). If this is the case, then the bad thing is the imbalance that you're not doing them highsteps on the right feet (left hand), and this is because your left arm is too weak (bad), or that the routes in the gym don't have as many such sequences (not a problem).
The wear could also occur, you you do lots of high reaching with the left arm from a diagonal position (on left left), meaning that you flank a lot with the right foot. This will also create considerable amount of wear on the inner edge of the right shoe. As with above, cause can be the routes or strenght/flexibility imbalance.