I think with a fully suspended table like a Linn LP12 the dustcover is less likely to color the sound, but with a non-decoupled plinth it’s much better without the cover or at least with cover up. I have seen the static attraction effect at work myself so that’s another reason to go up or off. My WTT/TA has an unhinged “cake cover” so it gets removed for playing every time. I once had a Technics SP12 with a heavy rubber plinth and the dustcover really degraded its sound quality when down.
