No, a username is not spam.
The user account is not engaging in any spammy behaviour that I can see. Yes, the answers are not the highest quality and voting already reflects that, but they are on-topic and do not contain any overt promotion to qualify as spam.
Yes, the user account uses the About Me to promote the company, and the account links to their homepage URL, but such links are marked as no-follow. And the post quality is such that I'd more see this as a anti-advertisement for the company services anyway. It is not against the ToS, certainly. Take a look at CommonsWare for a user doing a much better job at using his account name to promote his company; this method of self-promotion is perfectly fine.
If you do find an account with a more overt spamming purpose (fake Gucci handbags!), flag a post for moderator attention using the 'other' link and explain your suspicions.