Most of my alters "sign" their name at the bottom of texts they send, but you can tell them apart sometimes without it.
Cassie doesn't "sign" her name at the bottom. But she does only text in lowercase letters, doesn't used any punctuation, and tends to have some spelling mistakes.
Kat swears a lot, both when she talks and when she texts. Usually, if the f-bomb is dropped more than once, people know it's Kat who's texting. She used to text in all-capital letters just like she writes, but people kept thinking she was yelling at them or something, so she's mostly stopped (mainly just to not have the annoyance of explaining that she's not yelling or mad at THEM).
Rain uses correct punctuation, capitalizes everything that should be (so no lowercase "i's"), has perfect spelling, and usually texts how she speaks, so it has a very "formal" feel/read.
L.C. and Luna, well, you can usually tell when they're texting because most of the time, they start bantering back and forth with each other playfully and leave the receiver of the text message completely lost and confused. You can also kinda tell it's them because they'll swear more than me, but not drop as many f-bombs as Kat does. They also don't care whether a letter's capitalized or not, and they don't care about punctuation (except obvious stuff like periods and commas).
(Trying to think of who else has texted from my phone...)
Rebel's kinda like a mix of me and Kat. She swears more than I do, but not as much as Kat does.
Dallas usually texts things like "man", "bro", and "dude". And he'll usually text something dumb that he thinks is cool, like a comeback he comes up with or song lyric spoofs or something.
Damone texts more than he speaks, but he still doesn't text much. And he has his signature greeting of "Hey (blank)", and that's all he says until (blank) responds. He'll also text things like "man", but unlike Dallas he never says "bro", and doesn't say "dude" nearly as much.
That's everyone I can think of who's texted on my phone for now... There's probably been more but I can't remember right now. Oh yeah! "Hannibal" texts just as he speaks, and is like Rain- perfect spelling, grammar, punctuation, etc. Now I think that's it.