Based on the research I've read, one of the most valued skills for workers is communication/teamwork.

I'll speculate wildly that the loners who perform well at these tasks don't have the leadership/teamwork skills that are so highly desirable.

Almost all of the programming competitions are individual, one of the most prestigious (ACM ICPC) though is a team based programming contest.

The team can be lone-wolf organized thou since (for on-site competitions) each team only has one computer. The one I did we were 3 in the team. We divvied up the problems and each took turns hacking out the solution. Yes we consulted each other on the solution we were doing but mostly we worked on our own problem. This might have been a defective strategy since we missed the top ranked team by one problem, but had 3 nearly finished solutions when the buzzer rang.

That's Google, so probably quarterly review scores.

Have other people look at your code? If it's easy to understand, to modify etc - it's good. Otherwise, less good.

assuming it works in the first place.