Systematic effects involved in estimating the IGM transmission for different Lyα line profiles. The intrinsic profiles considered (shown in the grey inset panels) are composed of a single (left columns) or double (with a fraction of 30% and 70% of the total flux contained by the blue and red peaks respectively, which have an equal but opposite velocity offset; right columns) Gaussian profile, either regular (top row) or asymmetric (Shibuya et al. 2014; bottom row). For each intrinsic line profile with a given FWHM and velocity offset Δv_Lyα (indicated by open circles), the corresponding observed velocity offset and convolved line width (filled circles) are connected by grey lines. The colour of each point shows the ratio between the estimated and true transmission, T_est/T_true. A horizontal dashed black line indicates the fiducial spectral resolution of R = 1000. Black hexagons show the JADES LAEs (upper limits indicating the line widths have not been deconvolved) considered in this work.