Two simultaneous, differently-altered pitches a second apart need their accidentals vertically staggered, not just their noteheads horizontally offset

When the seconds-apart offset above is applied, each notehead may still carry its own accidental. If both notes need an accidental at that onset, the two accidental glyphs must be staggered vertically (one further left/higher than the other) so neither one visually reads as belonging to the wrong notehead — a plain left-of-notehead placement for both, with the noteheads already horizontally offset, would put one accidental directly beside the OTHER voice's shifted notehead.

Two accidentals rendered at the same horizontal offset from their respective (already-offset) noteheads, so the accidental belonging to the voice whose notehead was shifted right ends up sitting on top of, or immediately touching, the other voice's unshifted notehead or its accidental.

Gould, Behind Bars, and Read, Music Notation — general accidental-clearance and multi-voice accidental placement guidance; this specific case (two accidentals stacked outward from a seconds-apart pair) is standard practice in SATB engraving and is what VexFlow's `Accidental.applyAccidentals`/ModifierContext machinery is DESIGNED to resolve when both notes are members of the same joined-voice group (see shared-stave-notehead-second-offset), but is not independently verified against real accidental content in Gradus's own test fixtures.

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