Seems to me like Jarkko Oikarinen or one of his crew invented hashtags, no? Denoting the context of your communication with something like #warez or #hack significantly predates web2.0.
Rather I think Twitter-style hashtags take inspiration from IRC channels in the format of #topic
Because channel names are not hashtags. The syntax is purely because IRC is a text-based protocol, so you need a special way to distinguish channel names from regular text.
That use— to define IRC channels— seems distinctly different than Twitter hashtags to tag individual posts. I wouldn’t be surprised if hash tags started as a nod to that, perhaps even jokingly, but I don’t think you could consider them a descendent.
Because channel names are not hashtags. The syntax is purely because IRC is a text-based protocol, so you need a special way to distinguish channel names from regular text.