There appears to be a subtle sign of a generation gap between what older and younger Americans believe is the proper way to use periods and commas with quotations.
As mentioned at this site, in the U.S. the standard is to put end-of-sentence periods and quotation marks inside the sentence (even if they’re not part of the quote). For instance, “I think this is an outdated rule.” This rule was put in place (this may be a myth as the linked blog mentions) because of the fragility of the period and comma pieces for typesetting many years ago. However, today’s youth have probably never used or maybe even seen a typewriter (other than using one as a toy like I did when I was younger), and that’s why more young people out there see the illogicalness of this rule.
The U.K. follows the more logical rule of putting any punctuation that is not part of the quote outside of the quote marks. In places such as Canada (the linked blog in the previous paragraph is from a Canadian) the standard varies. (See the paragraph below for an example of the use of this style.)
Here in the U.S. I have heard older folks complain about how those younger often prefer the more logical style. I agree with them, and thus henceforth on my blog I will be putting them outside of the quotes using the “logical style”. (Up until now I’ve avoided writing sentences with quotes at the end on my blog to dodge this issue). By the way, I composed this blog post in Microsoft Word (and then did a cut/paste) and Word recognizes both styles (no green line either way). One of my favorite game shows (Jeopardy!) has adopted the logical style themselves (as discussed in this thread from January 2007 on the show’s message board).