Ok guys

Ok thanks that was my stupid question like I said more of a curiosity 

I do not use dust covers at all

Not using a dust cover is a sure way to destroy your records but it is great for the record cleaning industry. I never clean my records. Don't have to.
As for sound that depends on the turntable and the dust cover. This may be the reason there are so may opinions. Most turntables do not come with a dust cover.  Those always sound better without if you catch my drift. A suspended turntable like the SOTA always sounds better with the dust cover down. The sub chassis with the arm and the platter are floating inside so the dust cover is not connected to it. The dust cover attenuates the noise in the room 20 dB or so, like having hearing protectors on.
Unsuspended tables with a fixed plinth might have a problem with the dust cover attached directly to it. Close your eyes and have a friend or spouse raise and close the dust cover to see if you can identify when the dust cover is down. If not, you are in business. Same if it happens to sound better. 
Playing a record generates thousands of volts of static. The record becomes negatively charged but dust is positively charged. So the charged record pulls dust into the groove like a magnet. If you use a dust cover and a conductive sweep arm this does not happen at all. Records do not get noisier and you never have to clean them. Preserving your record collection is paramount more so than even sound. 
Making a dust cover for odd turntables like a VPI Avenger or an SME is not hard at all. You just hinge the dust cover to a plate on which the turntable sits. If you can not do it yourself these guys would be glad to. 
https://www.displaycasej.com/custom-audio-covers  A turntable covered in dust and grime is a travesty. Precision instruments should not be treated this way. To me a turntable like the Clearaudio Statement is worthless because you can't put a dust cover on it. But I can put a dust cover on an Air Force 1:)

Dust cover off and placed in storage: 4
Dust cover on at all times: 1 (Mijo)

I added my vote for no dust cover to those of Chak, Slaw, and Miller Carbon, for a total of 4.

To be clear, leaving a dust cover attached to the plinth in “up” position is also a no-no. Lets keep a tally.

I still use the SOTA Sapphire turntable I purchased in 1983, which btw still works as well as when it was new. I can pound its plinth with my fist with light to moderate force while a record is playing, with no audible consequences. Given that, it’s hard for me to imagine how vibrations induced in its dustcover and conveyed to that plinth could have any audible consequences. So in the case of that particular table, and presumably its later incarnations as well, I agree with Mijostyn.

Regards,
-- Al