Out of curiosity, why? The amount of times I’ve banged out a Reddit or hn response and deleted it is almost uncountable. Why do you bother replying to Reddit comments?

You need an account just to browse old.reddit.com now, there's some extensions that do an okay job of emulating it but it's not quite the same.

They didn't even say they reply to anything. Perhaps they use it entirely to post local news stories.

Your behavior is even stranger than that which you are questioning. The fact you take the time to type out the response means you also feel the urge to respond, and that urge is strong enough that you don't stop yourself before starting, even though you know you are likely to just delete before sending. It's odd that you would ask why someone would reply to a comment when you should already understand why someone would do that: because they feel the same urge you do, and don't have the compulsion to stop themselves before sending.

Unless you have a reliable social network with reach, reddit is still the reliable way to get some answers for one niche or another.