whoa it's surprising that calling someone just adding -ka gets you Russians shy!
Ehmmmmm, not shy, but calling -ka between men surely causes suspicions about their homosexuality. Between girls it's always ok, between men and women it depends on situation. Khm... I call -ka all my female friends and they seem to be pleased. And many of them call me "Vitalichka" (-ka from Vitaliy) though we're not lovers. I do say calling -ka not always means love and all. Just close relationship.

As I understand your language, you basically add -kun and -chan to men and women names to show some formality. Names without them are permitted between close friends. I think the same with -ka, but -ka is also caressing thing, not just a sign of friendship.

And can I recognize you basically call friends/familiar people with those nicknames originated from the basic name?
Yeah, they're not nicknames actually. Just a familiar "branch" of naming.