Comma usage question - "who, though"

First up, apologies if this is a repeat. I posted this yesterday as an anonymous user and now can't find it.

I'm confused about whethere one of the commas in this sentence is necessary:

The real revelation was Mr Barton, who, though a teetotaller, proved himself deeply knowledgeable about whisky.

Is the comma after "who" needed? I thought not - on the grounds that there shouldn't be a comma before a parenthetical element if it is preceded by a conjunction/joining element. Of course, "who" is a pronoun, not a conjunction, and "proved himself deeply knowledgeable about whisky" isn't an independent clause, but still it sort of feels right without the comma after "who".

Thanks in advance for all advice.

L