... what makes porting undesirable?
For smaller caliber guns (.380, 9mm), there's not enough gas volume to really have an effect on muzzle rise - which is all porting will control unless the porting is specifically designed to have a muzzle brake action as well.
I have a Detonics Combat Master that I ported in 1984 when I owned an electrical discharge machine (EDM). The porting made a noticeable difference in the muzzle rise, but had no effect as a muzzle brake as you really need multiple ports that are angled. There really isn't enough room on a short pistol barrel to create a ported muzzle brake.
If you'd like to see what needs to be done for a ported muzzle brake, look at Les Baer's website for the Enforcer Muzzle Brake on his .308 rifles. The design works and reduces a .308 to between a .223 and .243 level recoil - but, it's also about 2.5 inches in length.
I also have a ported .41 magnum pistol and a ported .44 magnum. The ported barrels on both of those guns have the effect of reducing muzzle rise and allowing faster and more accurate follow up shots. The porting on either gun does nothing to reduce recoil.
One of the Internet memes that gets endlessly repeated as if it's gospel is that a ported barrel will blind you at night because of the muzzle flash coming out of the ports. Not true.
The ports should be put on a pistol barrel at 45 degrees to the center axis of the barrel for the most effect. High speed videography of the muzzle flash shows the muzzle flash between a ported barrel and unported barrel to be nearly equal - a big ball at the end of the barrel.
The flash hider on an AR directs the gasses radially and if you've seen them work at night, you have muzzle flash coming out of the ports - you should be blinded by that as well, and you're not.
If you're not blinded by the muzzle flash from a standard barrel, or a flash hider on an AR, the porting on a pistol isn't going to blind you either. If the ports are at 45 degrees to the bore axis, the flash is directed away from the front sight and has no affect on night vision anymore than the ball of fire normally created at the end of the barrel.
However, there can be one potential detrimental aspect to muzzle porting if the gun is fired directly alongside your body as the porting could vent gasses directly into your body.
But, again, you won't find people warning not to do that with a revolver and there is a lot of gas vented out the side of the gun between the cylinder and the forcing cone.
If you're worried about that aspect of porting, then you should be worried about the same type of thing with a revolver.
None of this is theory, I've looked at porting, muzzle flash, etc. using high speed video in 1984 when I ported my Detonics Combat Master specifically because I wanted to see how it was working.
No, I can't post the video on the Internet. It's all on 3/4-inch video tape and I haven't had a 3/4-inch video deck for 25 years.
