It's easy to cut yourself with a handsaw in a tree, because you are often closer of your work and don't have many choices to reposition (or don't want to).
The saw can jerk on the wood and get you sideway like any saws for home work, except that it doesn't give a simple scratch but it goes directly to the bone.
The main way, though, is to cut the limb sooner than you expect. The saw cuts so well, that it finishes the job before you know it and you don't have the time to stop your movement, the saw cuts through and ends on a knee or your other hand (or rope or ...).
You think that you have all the things under control but not that much. It can get you even if you take care.
I know it, all my new saw-pants got their first scratches by that way.
The gloves can't do much to protect your hand, never put your hand near or under the handsaw, even if some wood is initially between them.
For example, this stupid small limb just 1" out of reach over your head. The other limbs are too thin to step on, so with a hand you catch a small crotch just under the target to stabilize and drag yourself a little, while you extend at max to cut the taunting limb. You can bet that the holding hand will soon be unhappy to do this job !
Take special care, this tool doesn't need a powerful engine to hurt you.