I found an interesting bug today.
I have two users who were logged onto my server at the same time, "Radio", and "Radioactive".
I tried to make "Radio" invincible with the "godmode" command.
I noticed then when referring to the username with double quotes, godmode was actually applied to "Radioactive". If I removed the double quotes from Radio's username, it would properly apply godmode to Radio as intended.
I only noticed because I have automation that watches logs and runs "godmode" on users. I had users with spaces in their names which broke my automation. I added double quotes, and this problem cropped up.
I could check for spaces in the username and alter my command accordingly, or even check the currently logged in list for matching initial substrings, but I'm not sure it's likely that two users with usernames that start with an identical substring and both have spaces, will be logged in at the same time.
Either way, it seems like there's an issue with godmode command's username matching logic. I was unable to test other commands.
# Results in Radioactive becoming invincible
/godmode "Radio"
# Results in Radio becoming invincible
/godmode Radio