The principle
Appearing better than others is always dangerous, but most dangerous of all is to appear flawless. Envy creates silent enemies; an occasional, harmless flaw deflects it.
The application
Total polish reads as a threat. Display one small ordinary failing — a hobby you are bad at, a regional accent you have not erased, a thing you admit you do not understand — and the room relaxes.
The defensive tell — how to spot it being run on you
When a colleague seems flawless in every dimension you can observe, the polish is almost always partly performance. Notice this without resentment. The constructed perfection is itself information about what they think is at stake.