Not if it’s half choked.

To start the motor from cold, you’d have to lock the throttle open. The button sticking up on the top of the handle says this isn’t locked open, otherwise it would be down.

So, either the motor is cold and won’t start in this situation, or it’s hot and it will

If it’s hot, it depends on the carb settings if the motor revs up slightly on starting

Usually on older chainsaws, the chain will move jerkily on starting due to age, so worse case scenario this guy will get his trousers stuck in the chain and crushed/torn bollocks

That said, obscured by his trousers is the chain brake. If it’s forward, the chain definitely wouldn’t move anyway

Just someone that’s been using chainsaws for 30 years

A determined idiot could definitely do this to themselves.

Only if the clutch etc. is working correctly. But damaging amounts of power are not going to happen unless that Stihl is really about to fall apart.