Category E_bl. Panel a): typical continuum-normalised Hα profile for objects in this category (a spectrum without detection of prominent nebular emission lines was chosen for clarity). We also plot each Gaussian fit (g₁,g₂ – dashed, g_n – dotted) along with their sum (thick black-white line). The horizontal axis is centered on Hα at 6562.8 Å. Panels b) to f): distribution of fitted parameters for all the sources of this category. Parameters for the nebular component are only shown in panel c) as a reference point for zero wavelength and the number of spectra is therefore different for that histogram, since not all spectra have the additional N flag. Indices b,r,A,E denote blue (shaded histogram), red (thick-lined histogram), absorption (shaded histogram), and emission (thick-lined histogram) component, respectively.