That has become a very common thing, though the moderators are very quick to identify these ANN bumping people who does it for money. I've seen ICO bounties have a special amount of rewards reserved for ANN bumping service, embarrassingly some bounty managers even without any hesitation or realization (!) ask bounty hunters to get paid for posting replies on the project's ANN thread. But since forum admins are very well aware of this, some ICOs take their social sites like twitter or telegram to tell their followers to bump their thread. Sadly ICO that is most likely to scam people follow this illegal way. Have a look at this Megatron ANN thread
https://bitcointalk.org/index.php?topic=3133601.0 You will see a lot of one line shitposts from a lot of members, most of them are newbie accounts or junior members and since Megatron got exposed as scam, these accounts have not been seen online on the forum.