The rules are still you can vote for whoever you want for whatever reason you want.
After HF21, You can now give 2.5 (250%) full downvotes each date without using the voting power usually saved for upvotes.
This means we are able to become the opinion police without losing curation or using voting power. A lot of people have an opinion that they will downvote bidbot abuse. What is considered abuse varies.
Some people consider anything above 2x your organic reward as abuse. That means if your organic reward is 2sbd, you can only bid up to 2sbd more without inviting downvotes. Orthers say 10x, and others say no bidbots whatsoever
Bidding is downvoted especially on junk.
What is junk? One mans trash is another man's treasure. Personally I would avoid bidding on anything that takes less than an hour to produce.
In my case I am just going to stop bidding fot now since my average rewards have actually increased from an ROI perspective.