Gumbo filé - Yay or Nay?

Nope.

File in my world is on the table as a condiment folks shake some on their gumbo if they wanna. Fresh ground it give a good flavor. YA gotta be careful though too much in ya gumbo can be bad for ya. It's Ground sassafras leaves so google it and make your own opinion.

Probably used more in Creole gumbo than Cajun, so no.

Add it at the table. Just a pinch.

I buy it in a baby food jar. Put a little when I'm making a gumbo and add a little when I serve myself a bowl. Flip that spoon over and use the handle to scoop out a little bit.

My folks are Cajun and they use it on chicken and sausage gumbo, never on a seafood gumbo. They like thin gumbos and it isn't a thickener to them, just flavor. My dad always has fresh stuff.

Parfois...

Yes.

We add it at the table, but don't cook with it.

Chauvin-style gumbo, AKA "file' gumbo" is basically a no roux gumbo where file' is a vital ingredient. So, yes.