I can confirm that using
#startup and
#startups does
not ban you on Twitter!
However, I did notice the other day that someone (not a domainer) sent out adult content with a whole bunch of unrelated hashtags including as I recall startup. I certainly hope they banned or restricted that account, but they had about 30 hashtags as an obvious way to try to get bots to retweet it (that a startups or maybe it was startup hashtag one did, is how I remember it was on the list)
For anyone that runs automated services, retweeting via hashtags without a human moderating it is dangerous.