I have a different perspective. Looking at the original post, [1] it wasn't labeled "Show HN" or posted by the project's author (antirez). So my first read on seeing it in the HN front page would be "hey, I found this cool project". And these people commented with links to similar projects, which I take as something like "if you liked that project, you might like this one, too", or "I wonder how these compare". I find that sort of comment helpful and curiosity-inspiring. Very different from "you shouldn't have bothered writing this when some other project exists". I can't tell from the date-resolution timestamps but they might well have been posted before the author showed up in the thread.
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These are the sort of people whom you invite over for a nice dinner and they ask why didn't we all go to The French Laundry instead.
I have a different perspective. Looking at the original post, [1] it wasn't labeled "Show HN" or posted by the project's author (antirez). So my first read on seeing it in the HN front page would be "hey, I found this cool project". And these people commented with links to similar projects, which I take as something like "if you liked that project, you might like this one, too", or "I wonder how these compare". I find that sort of comment helpful and curiosity-inspiring. Very different from "you shouldn't have bothered writing this when some other project exists". I can't tell from the date-resolution timestamps but they might well have been posted before the author showed up in the thread.
[1] https://news.ycombinator.com/item?id=494649