Not to mention the hours that go into making every chapter start on the same page (right or left, depending on style,) making facing pages bottom out, adjusting those pages so there are no widows and tombstones, and making your adjustments + or - standard line length progressively, so that you don't have two lines long showing through the next page which is two lines short . . . . yeah it gets validated to standards over 300 years old . . . and the rise in eBooks has allowed amateurs to break all these rules, upsetting standards publishers have been working with all these years. -1 point again for the Internet . . .
Center as an attribute or a standalone tag is content mixed with markup, that's why it's deprecated, and why it's unnecessary.
Do valid html icons make you jealous, is this what annoys you about them? :-) I find "valid html" icons annoying only when the page doesn't validate . . . which is most of the pages I see with them.
Absolutely not, I LOVE validation, if for no other reason, for this one: it is the gateway to the solution of the bane of every developer, the doorway to freedom from the one thing that drives us nuts, cross browser compatibility. Validate your pages, you're 90% there. It's more of a tool than an acid test.