No, mashing out makes it only give around 3-7% damage, but makes it an edgeguyard oppoturnity...
I also thought that, but there's a problem with this.
If Marth grabs them in the middle of FD (or near an edge, but faces the other side) and their % are like >100 you will have to mash a long time and will gain lots of %s until you're at an edge...
So it can be really bad.
Also, afaik Marth can do it to Lucas and Ness and Charizard only on Ness. Squirtle can also do it and it's even worse than with Charizard (since Chari moves forward quite a bit while grabbing). Not sure if Squirtle can do it to Lucas.
Bowser could do it, but he has 15 frames during his pummel where characters can air release... Does anyone know if Marth has a few frames where you can air break?
And DK could technically also infinite Ness and Lucas, but they can change the side in which they break free, so they could probably get free...
Grab release to an attack is allowed on them though, right? (even if those "infinites" get banned)
I don't think it should be banned. I feel like you can avoid it
![Oh Well :ohwell: :ohwell:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
(avoid FD, stay on platforms/at edges and they even have projectiles while Marth does not).