Re: N/l merging... Is it that new... or has it been around for a century?

I agree with Mr Chiu's observations with the vowel after the initial determining pronunciation.

I'd have to dig out my copy of Modern Cantonese Phonology to see what it says, but my instinct is that any correlation would have a high probability of being related to vowel position as shown on the IPA vowel chart depicted here: [en.wikipedia.org]

-Tony