Distribution of axis ratios of log(M/M_⊙) > 10.85 quiescent cluster galaxies in the probed cluster regions across the whole cluster sample (red shades) and in the reference field at 1.3 < z < 1.8 (blue shades, as indicated). For both cluster and field samples, darker (lighter) lines correspond to excluding (including) sources within ±0.1 mag around the quiescent vs. star-forming classification border. Error bars on the fractions over the whole population (binomial, Cameron 2011) are slightly offset for clarity. For comparison, the axis ratio distribution of star-forming field galaxies in the same mass and redshift range (grey line, errors within line width), and for 1 < z < 1.4 cluster galaxies in the same stellar mass range from Chan et al. (2021, hatched region, see text for details) are also shown.