@kyu3a This is against the Terms of Use already. Users of Vivaldi Social are still under the terms of vivaldi.net
8. Follow the Terms of Use and Code of Conduct of Vivaldi.net
"Post content with the sole purpose of driving traffic and increasing the search rankings of another website, product or service."
"Distribute spam or unsolicited commercial content."
"Facilitate gambling or betting."
https://vivaldi.com/privacy/community-terms-of-use/
And many more rules including automated posts, bots etc.
If you see content like that, make sure to report it to the VS moderators (I'm not one of those).
But: Also make sure that's it's actually from a Vivaldi Social user, if it's just on the "Other servers" or "All" feeds, there's usually little that can be done - unless it's all from a specific federated server, which can then be blocked from federation.