"Does glow fuel damage grass or not ?"
I believe it does , having seen (caused) that type of "bald spot" damage in the past with spilled fuel . I now have an electric pump with a return line to the fueling can so no fuel spills during fueling (with both my RC and CL planes) .
Heck , I've caused bald spots in my own lawn by spraying hornets nests with those canned Bee sprays that'll spray up to 20 feet , and having the liquid drip out of the nest and onto the grass . I imagine pretty much most chemicals will damage pretty much most living plants , maybe Monsanto needs to develop a strain of grass that's methanol resistant ?