Grade debates are inherently pointless.
Arguments about whether something is 5.12d or 5.13a (or whatever) are as unproductive as debating what a specific color looks like. Yes, while each and every color contains an empirical, measurable reality, which is its wavelength, precisely how that wavelength is “seen” by your brain may be different from one brain to the next, especially depending on the number of hallucinogenic substances that you have ingested that day.
Perceptions of climbing difficulty are just as personal—hence, this phrase, often shouted at the end of the rope, or face-down on a crashpad:
“That move is HARD FOR ME!”
A surprisingly even keel look at the arbitrary nature of climbing grades from Andrew Bisharat. Normally his writing isn't quite my taste even though I think he is a good writer. He goes through a very brief history of the hardest climbers of past and present and points out how claiming that someone is the "first to climb..." is almost pointless. A 5.11 in Yosemite can fee like 5.12 anywhere else in the world and climbing styles differ between crags and our favorite destinations. Don't get wrapped up in the grade...just enjoy the climb.