I agree with your comments.and would go further in that all people have a capacity for both honesty and deceit whether it’s in an online forum or in the ‘old fashioned’ face to face communication. There’s maybe also some truth that when we’re first expressing our interest in someone we cherry pick the stories and descriptions that won’t send the person we’re interested in running for the hills. A year and a half after my ex-wife told me she’d been conducting an online affair and wanted to leave me, I’ve dipped my toes in the online dating world. For the most part I’ve found it like a grand-scale game of Guess Who. Photo after photo, world travelling, yak wrestling, bungee jumps from..... surely there’s got to be a good man left out there?
Perhaps it’s been lazy of me not to write longer messages, maybe I should write out a relationship cv to cut and paste when someone’s picture makes me stop and take notice and wonder what they’re like in person.
I don’t know if there is an etiquette for the online dating scene but when I have received the very occasional like and had no interest, I’ve thanked the lady for hers and politely declined.
Maybe that leads to another debate. Do people feel more rejected by a written no thanks or the lack of reply altogether? I know I’ve preferred and respected the former most.

Sometimes a "Hi" is just a simple feeler put out to someone who has not given you much to go on. For example if their profile says "lets talk about it" what more can you say? A "Hi" back says "I do not find your profile repulsive either." You live reasonably close and are of similar age, background etc.
I always respond to all msgs Although it is a very difficult medium to correspond in. Often you feel that each sentence is going to be scrutinized and annualized like a job interview or a court statement.