Unless the flagstick itself is unusually thick or is moving in the wind I will leave it in.
I feel it gives me 2 advantages, albeit they are probably just in my mind.
Advantage 1 - it narrows my focus on the centre of the hole.
Advantage 2 - I hit my putts a little firmer.

Love the Gulf Racing 'Scotty' headcover.

I don't really understand all of the sudden discussion on this subject. There are a few obvious points such as it no longer being an added penalty stroke for striking the flagstick. The other main one being that no one is now needed to attend the flag for a long putt, thereby speeding up the game.
But surely it's not really any different to chipping from off the green. That has always been down to personal choice and how one assessed the slope, weather, etc.etc.
No one used to have debates about that.
One small observation. If one is putting downhill, the gap between flagstick and the higher edge of the hole is actually reduced, thereby reducing the chance of the ball dropping in the hole. Likewise on side slope putts.

In for me apart from close putts but I have been bitten a few times now by a fast moving ball ricochet of the stick but the speed the ball was moving it wasn’t likely to drop with the flag out either

In for long putts over say 6ft and out for anything inside my putting been that bad lately I doesn’t really matter

Out, out, out , sometimes tended but in never leave it in. The reasons are harder to read a putt, can make off centre cup putts miss, not advantage on a good putt on disadvantage and it just looks and feels strange.

Flag out for all putts. And for those longer putts an spotter to pull it out
Just my opinion been out lately and to my wife noticing that fellow golfers using the flag in rule works for most but take an good look at the cup insert and how these are been move from trying to haul your ball out when leaving the pin in.

Just an observation what are most thoughts about this or am I’m clueless?

Flag in for me unless playing with others and they want out. Just to speed things up on the green.

I find it easier for lining up putts. Shadows are your best friend on the dance floor.