I've noticed a few times that tone has come up a lot in RPGs. Like a GM pointing out on a repeated basis that their RPG is meant to be light and not dark, or how someone is complaining about angst in a character's back story. It's led me to think of how people feel about how dark or light an RPG should be. Is it of any concern to people or something that's easily ignored?

Most roleplays tend to be neutral about this though. For example in an action fantasy rp like slaying dragons, it is fairly common to see both light hearted characters as well as those with grim pasts.

However, if you were making say, a roleplay about a pokemon adventure, then putting in a tragic past about being raped is clearly not suitable.

I usually don't find having a light-hearted character in a dark rp or vise versa to be too big of a problem most of the time, but often times I think tone is compromised in other ways, like technology level or power level of the characters.