Erm, it won't affect the code in the slightest.

You are absolutely correct - tags like <b> and <center> are supposed to have closure. On the (not so) odd occasion that they don't, however, the performance of the script will not be affected. Should the code have been intended to validate HTML then you might have a point.

I'm not sure how that will affect your attention to detail, but I did want to point out the misunderstanding in your interpretation of the code header.