Edit: hey hastagstartup.co downvote brigade, hashstartup.co is still available. So is hashstartups.com which is even better.
So I downvoted because I wanted to signal that I'd like to read less content like that on here. I went and checked the HN guidelines on content, and here's a few points which I felt supported the downvote:
"When disagreeing, please reply to the argument instead of calling names. E.g. "That is an idiotic thing to say; 1 + 1 is 2, not 3" can be shortened to "1 + 1 is 2, not 3."
"Resist complaining about being downmodded. It never does any good, and it makes boring reading."
"Please don't bait other users by inviting them to downmod you."
And now I have contributed in uselessness to this comment thread, the cycle is complete :).
I get what you're saying, but its still fair to call it a hashtag, and for them to call it hashtagstartup.
Solid hacker news etiquette there, by the way.
Also, you get what you dish out. Saying its "dumb" is what earned you the 15 year old in me. had you said something like "i disagree with their use of the word hashtag" it would have given an entirely different tone, don't you think?