As founder and (so far as I am aware) sole member of the Society to Promote Uniform Rules for Symbolic Enclosure (SPURSE), I must resptectfully disagree with the inclusion of punctuation that is not in fact part of a quotation within quotation marks. Yes, this is traditional, but traditions change when faced with new circumstances.
The new reality we are faced with is that this arrangement is likely to rankle anyone forced to discipline themselves about the precise placement of symbols within syntactic enclosures, usually for the purpose of math or computer programming. Those so disciplined now represent a substantial fraction of the population, and their (our) cognitive dissonance far outweighs the faux-moral imperative of tradition.
In my opinion, any placement of punctuation that is not part of a quotation adjacent to a quotation mark, whether inside or outside, is awkward, and to be avoided if an acceptable workaround can be found. If a comma is needed, use a dash instead, and separate it from the quotation mark by a space character. (Always surround dashes with space characters!) Any situation in which a comma would be needed following a quotation usually warrants a dash anyway, and this is better than placing something within the quotation marks that isn’t strictly part of what is being quoted.
That said, what do you think about the use of single quotation marks to denote an expression that might commonly be heard or read, rather than a specific usage of it?