They're not paying you to move, they're offering a discount... Semantics aside, this is a pretty common thing for a competitor to do when something negative comes out about their competition (Either giving out blanket discounts regardless of social media or having you verify a tweet some how)

I understand the value of guerrilla marketing, but at the same time it makes them seem less credible.

Imagine if they offered a 75% discount for defending them or praising them on Hacker News! That would make any comment in support of GitLab suspect.

I think many of the #movingtogitlab tweets were sent before we even offered a discount.

They said more then 1000 were tweeted before they make the blog post. Now they have 2000 tweets.

I bet most of those newer 1000 #movingtogitlab has absolutely nothing to do with the discount.

Yeah but this type of advertising is really common on Twitter and not on HN.