Would an Isolation TT platform further improve my TT?

For turntables the primary problem is the resonant frequencies of the tonearm and cartridge are very low, circa 10-12 Hz - too low for the acoustic waves from speakers, but just right for very low frequency seismic type vibration, you know, the ones coming up from the floor. Thus, the tonearm and cartridge are excited by seismic type vibration in the range 10-12Hz. So, the answer is YES, turntables should be isolated. Final answer. 🔚

Which gets us nowhere, since it is still begging the question: How?

The obvious answer everyone comes up with is something soft. Think inner-tubes on the DIY cheap end, Seismic Shelf or whatever on the spendy end. The problem with all of those being they still need to be tuned or balanced if you prefer.

Less obvious is use something sufficiently massive and solid. Go massive enough and at some point the thing simply will not be capable of moving at any but the lowest subsonic frequencies. 

Its even possible, if you want to go to all the bother, to calculate based on dimensions and mass exactly what those frequencies will be. Or you could just build one, jump up and down enough to get it rocking, and make a pretty good estimate. Mine is way down in the low single digits.

There's another one the isolationists never seem to answer, and that is the question of: Which matters more- vibrations that are external, ie a part of the environment? Or internally generated?

The answer by the way is: Both. In many if not most, or maybe even all situations the turntable itself is the greatest source of vibration. Given the wackiness of some contributors this might be a good time to say for the record I don't mean during earthquakes. But most other times, just sitting there playing a record, even in your rickety room, the turntable itself is your main concern in terms of vibration control.

Which means, of course, that regardless of what you use or how perfectly it isolates you still have to deal with the question of the very first material the component rests on. Because whatever that is, is going to determine more than anything else the nature of the vibrations reflected right back up into the table.

That's why vibration control is not just words to say, but rules to live by. Isolation is only one aspect of vibration control. I seriously doubt it is even the most important.

The big problem with the “heavy and massive” approach is the entire building is moving, thus everything that’s not decoupled from it is moving right along with it. The mass of the building itself cannot withstand the enormous forces produced by seismic type vibration. “Resonance Control doesn’t work for very low frequencies or is very ineffective. That’s where isolation steps up to the plate. Pretty basic stuff.

What ever became of Torlyte? It was claimed to be stiff, but how stiff can very thin strips of wood be, even if fabricated into a honeycomb structure? There was one valid claim made for it: it's very low mass did not store and release energy. The stuff was like balsa wood!

For an iso stand stiffness is highly desirable for the top plate since a stiff top plate better resists bending forces, I.e., rotational seismic forces. This is why 3” maple boards sound better - generally speaking - than 1” maple boards. They’re stiffer. It’s also why some of the big commercial iso platforms use thick granite slabs for the top plate. It’s also why I use thick granite or bluestone slabs for my stands sometimes.