I forgot to mention an important fact about ICQ core code-base.

The core framework for ICQ was actually written by AOL long before ICQ was born. I.e. they developed general framework for scalable distributed systems.

So some comments in the code are dated as early as 1992.

I didn't mean formatting style but general flavor of how programs was written at these days. I can't put it into words, it's better to just see the code. Although, I'm not permitted to show the code.