Ever notice the interlocking joints on the pavement of a long bridge? The bridge needs to have some play or it will surely collapse.
The interlocking joints on bridges protect the bridge from thermal expansion/contraction due to thermal extremes and water/ice infiltration. Turntables are not exposed to such factors. A less relevant example would be difficult to imagine.
Movement certainly has a place in TT design. Nobody's denied that. Specifically, the platter must rotate at the selected speed, preferably with minimal deviations due to external inputs like stylus drag. Additionally, suspended turntables are designed to move under elastic, spring-loaded controls to reduce the amplitude and frequecy of vibrations. (BTW, this is the exact opposite of the expansion joints in a bridge.) Beyond these two specific types of movement, the less a TT moves, the better its sonic performance.
Air, on the other hand, has little practical relevance to TT design (air bearing designs excepted, obviously). Most vinyl rigs would in fact perform better in a vacuum, as that would eliminate airborne vibrations as a source of sonic mud.
This last fact highlights the absurdity of comparing a TT to a guitar or any other musical instrument, as none of them would perform in a vacuum at all.
I would think a heavy metal deadening ring would do just that, deadening the sound.
You might think that, but as you've apparently never actually used one, you're just speculating. Why post a question to people who've actually done the experiment, then argue with their results? Are you seeking validation of your flawed assumptions, or just trolling?