The notion that language was concrete has always bothered me as well, hence the quest for "dank" continues.
That said, I'm mostly here to clear the air about something rather important, and likely what is at the front of everyone's mind:
In my case I will accept either FLY, FLYs, FLsY, FsLY, FsLsY, FsLsYs, sFLYs, sFsLY, sFLsY, or even sFsLsYs.
Depending on the day, I think it's also proper to spell any of those backwards.
EDIT: Also, with the rise of WU LYF, I will also accept LYF but not claim their use of meaning applied to that acronym. Any deviation like the ones above in relation to that acronym are sound uses of grammar as well. Again, depending on the day, it is even proper to use WU FLY.