I'm pretty sure that's not what you think it is... if I write my interpretation of that username in proper japanese it would be コーヒー苦い (coffee bitter). it's written that way as you can see in the username when used as an interjection. in this case, the -i ending of the adjective にがい is dropped and the gemination of the consonant is used emphatically. にっが! is a common interjection in casual conversation. can we stop projecting western centric views especially when it assumes the worst and could paint people in a bad light