Regarding Persona protagonist, it'd be best to use those:

boy_with_earring
tatsuya_suou
maya_amano
protagonist_(persona_3)
female_protagonist_(persona_3)
yu_narukami

Protagonists with canon names like Tatsuya (in-game default), Maya and Yu (used in more than one adaption) should use their names. Protagonists without canons names like P1 and P3 (different names in various adaptions) should have their non-canon names like Naoya Toudou, Minato Arisato, Makoto Yuki, etc. as Aliases only. Same goes for Souji Seta, which is an Alias to yu_narukami.