The Grammar Nazis

"not regardless of..." vs "not regardless of..."

If we are talking about the eyes, then separately (mnemonic: because the anatomical eyes we also have are separate):

I can paint from memory, regardless of the original.

If you can replace it with "opposite", then it is fused (mnemonic: because "opposite" is fused)

I can draw despite the absence of hands: I hold a brush in my mouth or my feet.