Where are all these BIRs/TAs that stick lemon/garlic in their Madras? Not round here that's for sure. FWIW I think the addition of lemon/garlic was one of the things that marked out the better BIRs of yesteryear, the madras then being served either garnished with ground coconut or coconut chutney on the side. These days all you ever seem to get is a standard curry with extra chilli powder in it, no finesse at all.
So, for me, the combination of lemon/garlic/ginger and spices is what goes to make a good Madras, unfortunately the skills required to achieve the right result seem to be disappearing in direct proportion to the number of BIRs and TAs that are transforming into fried chicken/pizza/kebab joints.
Regards
CoR