Non-isotropic clumping can also favor ÒsidewaysÓ escape, and thus suppression of the bluest and reddest photons, if the clumps are oblate.  This makes lines more symmetric.
The Venetian Blind Model...
Oblate clumps might be expected from the line-force instability, since it is a radial forceÉ

On the other hand, prolate structures might be expected to develop from classical plasma two-fluid instabilities (Rayleigh-Taylor; Richtmeyer-Meshkov)