Ya, like people buying NEOS coins instead of NEO  Jeez, that would suck!

I found this about name lengths:
https://ethereum.stackexchange.com/questions/25619/is-there-length-limits-on-token-symbols

It seems that it depends on the exchange. As Gleb Gamow said above about 8 character symbols being the max on YTC-Sox.

Maybe there isn't a max number of characters, but perhaps for display and formatting purposes, individual exchanges choose the number of characters that best fits in their display format.