Syncopated off-beat accents are notated with ties spanning the beat, never with a single relocated value

A syncopation (e.g. eighth-quarter-eighth across two beats in simple meter) is written as separate notes tied across the primary beat boundary so the underlying pulse remains visible through the tie, not as a plainly-notated single note value shifted off the beat grid.

A quarter note is placed starting on the 'and' of beat 1 with no tie markers connecting it to any beat-aligned note, so the syncopated figure reads as an ordinary off-grid rhythm rather than a legible syncopation.

Gould, Behind Bars, ch. 'Notes and note relationships'; Read, Music Notation, rhythmic notation chapter, worked syncopation examples.

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