I agree, there have been a bunch of abusers on DTube. @crystalliu is one of it, not only he is spamming all 3 chains, the spam videos are marked as "original content" where it is clearly not.
The circle voting ring is even more worse, as the DTCs that are obtained can screw up Avalon blockchain consensus by voting up multiple "witness accounts" which do not have a node running, so it will constantly miss blocks. One of the accounts is currently ranked #6 and have been missing blocks for months. Given the amount of tokens that those accounts got, it is possible to vote up at least 3 accounts into the top 10 and make things even worse.
Perhaps the curation reward and content discovery algorithm needs to be worked on here 🤔