Thread:Bellamybug/@comment-16101931-20190205020327/@comment-12699193-20190206040613

That's the same one I'm talking about. The nonrestrictive clause ("which she flips to turn the lights on just before being surprised by Finn") requires a comma both before and after. Otherwise the main clause and the nonrestrictive run together (not sure what it would be called technically, maybe a run-on).

Think of a simpler sentence: The table, which is in the kitchen, is made of oak.

It wouldn't be correct to omit that second comma. It also wouldn't be correct to omit both commas, because then you would have to switch out the 'which' for a 'that' (not to mention that the meaning of the sentence would also be changed).

https://www.writersdigest.com/online-editor/which-vs-that