Chat prompts, like some IRC clients used to, suffix nicknames with a : to separate message from the name, so it could be they simply implied the "eyes" were already there.
iirc one of the Asian languages pronounces the number 4 as "ha" so instead of typing things like "LOL" they'll just spam 4 to respond to something funny.
The parenthesis thing is probably something similar. We've all got weird linguistic quirks; the digital era just dumps fuel on the fire.