Accidental glyph must not collide with the stem of an adjacent note or chord tone

An accidental's glyph must clear stems of neighboring notes in the same/adjacent voice and of other chord tones.

A close-position SATB chord with opposing stem directions has an alto accidental collide with a tenor stem in the same horizontal region.

Ross, explicit accidental-to-stem clearance discussion in dense multi-voice writing; Gould implicitly via the chord-stacking diagrams that exist to prevent this.

This rule is about where marks land on the page, so it can only be judged after engraving. Collision and spacing faults live here.