An example sentence under Definition of "expatriate" (verb)

Hello,

The comma in the example sentence followed by a clause is odd in this Definition of “expatriate” (verb) under TOEFL vocab test, Test # TOEFL/W4. I cannot make out why the clause follows the comma in the example sentence. Should it be only the comma that is followed by “still less tempted to expatriate himself” or is it because of grammar that a comma and “still less” can be followed by anything such as an independent clause, a phrase or a noun? As far as I know, “still less” is an idiom.

Here is an excerpt from the example sentence of Definition of “expatriate” (verb) under TOEFL vocab test, Test # TOEFL/W4:

Definition of “expatriate” (verb)
to banish; to exile; to withdraw from one’s country; to expel

Example

Winters in California perhaps thought himself securely distant from the seat of the infection; he never visited Europe, still less was he tempted to expatriate himself.

english-test.net/toefl/vocab … ns.php#low

Thank you.

Best wishes,
Bhikkhu1991a .

This may fall into a class of contrastive sentences where commas are accepted even though, following the rules absolutely to the letter, they may appear to result in a comma splice. For example:

“I didn’t ask you, I asked him.”