Well being a restaurant owner, I have faced both, FAASOS as their supplier or associate partner somewhere in end of 2015 (initially faasos used to outsource most of it's items to local restaurants, re-brand them and sell it at premium price. I guess now a days most of the items are made by their own kitchens now.) and a customer who gives negative feedback with both good and bad intentions.
First of all I would like to say even I had bad experience with faasos because of their behaviour and the language they used, that was the reason I pulled out as their partner/supplier (hardly after a month). So I am sure in this reply as well they were not trying at all to be witty and it was their usual self.
On the other side, even if a customer is writing a negative review with bad intentions (to bring your ratings down, to ask for some favours (in most cases extra chutney/pyaz) etc.) we the providers have to be politically correct. I myself know couple of customers who asked for favours (same...extra chutney/pyaz) and upon denying or asking extra money for extra things, they went online and wrote negative things about us. Now if we also start using same mind as of the customer then it will be very amateurish behavior on our part as it will give bad impression to our good/regular customers. So that's the cost one has to pay to do such businesses...to suppress your ego...just ignore or reply politely and move ahead. But again, not expected from FAASOS.
Anyways, I think they are doing better than other FOPs like swiggy and foodpanda (on profit/earning level and not on number of orders) i guess and if they concentrate more on keeping their customers they could go a long way.