Thank you for the compliment ^_^ I'm glad you found the post helpful.

This isn't a typo, actually. If you look at the documentation of the BSRR register (which is screenshotted in the blog post), it says of BRy:

> These bits are write-only [...] [Setting to 1] Resets the corresponding ODRx bit

So setting BR8 in the BSRR clears the ORD8 bit in the output data register. Because our LED is active low, this turns the LED on.

The indirection can make this a little confusing, I hope this cleans it up!