Here's what I consider to be a neat (and hopefully helpful) example typing quirks from two of my trolls:

(A bit of context: Phosza is essentially a ghost who has taken over control of Tirias' eyes, and speaks to him in his head. Their typing quirks are meant to reflect this dynamic.)

Tirias: he types l_ke th_s. essent_ally, he replaces all _nstances 0f the letter "I" (b0th cap_tal_zed and l0wercase) w_th an undersc0re, and all _nstances 0f the letter "O" w_th the number 0

Phosza: He types liike thiis. Iit's a very siimple doubliing of the letter "I". Iif II'm remembering correctly, he also occasiionally ends hiis messages wiith audiio fiiles so that he can "speak".

Phosza has some level of remaining psionic power that allows him limited interaction with the world, and in the case of typing quirks, he uses it to operate his own Trollian/Chittr account.