A mark's structural side is fixed by stem direction or part convention at authoring time and must never be silently flipped to resolve a collision

When resolving a local vertical collision, FLIPPING a mark's canonical side is worse than nudging the colliding glyph horizontally or increasing staff-to-staff distance, because a flipped mark reads as a different instruction.

An auto-layout pass resolves a dynamic/staff collision (vs-dynamic-staff-collision-multivoice) by moving the dynamic ABOVE voice 1's staff instead of increasing the stacked-layout's `systemVFH` or repositioning within the correct side.

Gould, Behind Bars explicitly warns against dynamics appearing on the atypical side of a staff for a given part as a default remedy; Ross, The Art of Music Engraving ties side-of-staff placement to established per-part convention, not per-collision convenience. Where some automated engraving tools DO auto-flip marks to dodge a collision, this rulebook recommends AGAINST that for Gradus specifically, because its content is pedagogical — a flipped dynamic or displaced articulation is exactly the kind of inconsistency a 15-year-old pattern-matching student would misread as meaningful.

This rule can be decided from pitches, durations and voices — no layout required. A validator can check it before anything is drawn.