Deck discharge

You can cut that piece out but you need to put a few spot welds around it to hold the shell together. Easy stuff if you have a look, no big deal. If you are careful cutting it out then its easy to weld back on.

If you are having discharge issues, cut it out and use super high lift blades. The come off a 48" or something deck with a catcher. Ive lost the part number sorry.
Heres a guy who had the same problems... https://www.youtube.com/watch?v=uz8gnPxUqk0

Bert is correct, it is simply a gusset. The majority of the refuse is coming out of the front of your deck, so it shouldn't be causing any discernable discharge restrictions.

take a second and buy some spray foam or a good wet mushed up new paper and mould the pice of corner you are thinking of cutting off, in other words fill in the corner from the inside and see if it makes a difference to your cut. This way you can mould a piece out of foam later and make it permanent.

Just my 2 cents worth.

Cheers,

EH!