I had the understanding that there are some textures that you shouldn't change, like wall textures and stuff like that.
yeah portal / cube textures are fine, the only thing that would be bad is like wall textures with "hints" on them or stuff like that
there was a brief discussion about certain asymmetrical cube textures possibly giving an advantage for the 11/12 cube throw in glitchless, as some orientations of the cube make the throw easier. I don't know if anything came of that though.
For future reference - the above was discussed but in the end it was dropped, they only give a very slight advantage and it would be pretty tricky to moderate.
An update has been released for SST that adds the command sst_portal_resetisg. This command removes Item Save Glitch and is to be used in place of restarting the game. This is a temporary solution while a more robust and legitimate one is developed.
The reasoning for allowing this is to make the ne