Is it when you hit the curve? A bit before? A bit after?
I ask because it is important to me as a player to create "realistic" characters. Not just a set of optimized stats and skills.
This is especially relevant in the context of soft skills. Intelligence and Charisma mainly.
Sindome and most games do a good job of putting guardrails in place around hard physical skills. While a player can present their character as being the pinnacle of physical fitness, the coded systems around Endurance, Strength, etc. will quickly sus out the truth of the matter.
Consider Charisma. That's really something that the player either has, or doesn't have. If you're a charismatic people person IRL, at what point do you intentionally go against your natural instinct because your character has a low charisma? When do you mock and get annoyed with someone that you, as a person, otherwise would naturally befriend? When do you say intentionally cringe and unacceptable things because your character, based on their stats, doesn't know any better?
Same with Intelligence. If you're naturally 120+ IQ and because of that are able to scheme and plot and strategize, what do you do when you're playing a combat character with a low Intelligence skill? Do you keep asking "Why?" when the why is evident to every other character in the room? Do you tell the smart people that they're stupid because you ICly don't understand anything beyond... smash face, steal loot?
The questions I asked are to provide context and examples of going against your character's best interests.
At what point is it "okay" to decide, I've put enough UE into this stat so that it's not a hinderance to my character's ability to function "normally"?