Up with this, I will not put!

I have a bone to pick with Tom and Ray. Well, not Tom. Just Ray. And not really, because Ray seemed perfectly aware that lots of bones will be picked with him this week. (I'm referring to the Magliozzis, of course – from NPR's CarTalk.)

It has to do with the answer Ray gave to this week's Puzzler. Here is the original question:

"Usually when the subject of a sentence is compound, and the components are connected by 'and,' the verb takes the plural form. For example, we say, 'Bob and his wife ARE planning to drive to Florida'... not, 'Bob and his wife IS planning to drive to Florida.' Likewise, we say, 'The vase and the book ARE on the table,' not, 'The vase and the book IS on the table.'

But, can you think of a situation where the components of a compound subject are connected by 'and,' yet the form of the verb must be singular, and not plural?"

Their answer won't appear on the Web until Monday, but it has already aired on the radio show (at least in Buffalo), so I'll spoil it here. Ray reports that when the two phrases joined by 'and' refer to the same thing, then you have a compound subject paired with a singular verb form, thusly: "My college room-mate and best friend is coming to visit next week." (Assuming that "my best friend" and "college room-mate" are the same person.)

Upon hearing this answer, Tommy immediately protested that this is not a compound subject, since you don't actually have two subjects joined by 'and', but rather two phrases that refer to the same singular subject. It also seems to me that, as written, the sentence-as-such needs commas around the phrase "and best friend", because otherwise it's terribly ambiguous. Anyway, Ray didn't exactly rise to a fierce defense of his answer; in fact, he conceded that CarTalk is likely to receive lots of angry mail from grammarians.

Now, I'm no grammarian. I tend to write by ear, and if I have something troubling come up, I gotta look it up like anyone else. (For instance, I shamelessly use words like "gotta", which no grammarian would touch with a ten-foot-pole even if they hadda.) So, for my more grammariable (I make up words too!) readers, does Tommy have a beef? Is that really a compound subject?