Really? There are several examples in the original post of traits and flaws to roleplay that might be appropriate for a character with a low Intelligence score. How is that "only play our self?"
Most of the examples aren't all that good, have little to do with intelligence.
These don't need to be role-played, they manifest when rolling to see if you are good at a task:
- Yes, knowledge is INT based, but is also affected by training/skill rank/proficiency. Meaning some one who doesn't know about a subject all that much isnt stupid. (but can be).
- Paying attention, this I can see being used for all 3 mental stats. Not paying attention to the environment (Wis), not paying attention to social ques (Cha), not paying attention to details in a math problem or while reading some text.
- Risky behavior, this tied to Wisdom, not INT.
- Lack of confidence (cause you think you are stupid), this is Charisma based.
- Entering a new culture and having issue communicating, Charisma again.
Lack of intelligence manifests as such:
- You know less languages, and/or have a limited vocabulary.
- You have issues with basic math.
- You often choose the simple solution to a problem, cause complexity confuses you easily.
- As said above, yes it can manifest as lack of Knowledge too.
- Remembering/memorizing is a problem.
- How your lack of INT manifest, depending on your other mental stats may vary.
- Don't get me started on how culture, upbringing, schooling, family, friends... influence your personality as a low INT person.
OP doesn't want us to play our characters as "Hurr-durr" dumb at 8 INT. And I will respect that, if you are insulted and at my table.
And to get to the original counter argument. Playing a character as very dumb is ableist, right? Then how about:
- playing low CHA, is it ableist to play a socially awkward, withdrawn from society, rarely talking to others, kind of person?
- playing a character that takes unescecery risks, makes bad choices (low Wis)?
- playing a very sickly character (low Con)?
- playing up the fact that you can't carry all that much cause you have low STR or are very clumsy (low Dex)?
We need to play up the stats when role-playing, else it wont be noticed or be memorable. Like in theater the actors have to make over exaggerated gestures, so that the audience sees and understands it. If we don't do so, then you are left with a character whos personality isn't influenced by their stats (which is fine in my book, that is another way to play your character).
Let players play their characters as they see fit, as long as noone is insulted at the table and everyone is having fun.