Hello.
"I upvote everyone who replies to my posts"
This is exactly the reason why these accounts are blacklisted.
Accounts "biyimi" & "precab" belong to one person although he claims that it is a "friend".
"yellow74" may be a different user but received the same list of accounts to follow and comment from "biyimi".
I am sure that you have noticed that most of the comments on your posts have been coming from the same group of accounts.
They exclusively comment on accounts that guarantee upvotes, not just your account. They have a list of dozens of accounts that they comment on daily while ignoring the rest of the other Hiveians.
Biyimi keeps sharing this list with others, so more similar accounts may pop up in the future attempting to farm your votes.
Sometimes you may notice that these "flatterer" comments may not completely make sense suggesting that the users did not read the post completely.