It would be abused as crazy. Expect retaliatory feedback against anyone that doesn't like the other person. There would be a similar problem like we have with the trust ratings on Bitcointalk. A scammer gets tagged for scamming and retaliates with bullshit comments.
Your idea is not bad but the community would make a mess out of it.
There are always two opposite sides and I know potential abuse but as I wrote I thought benefits outweigh negative effects and it is worthy to consider for real implementation of Tag/ Report buttons. It is a kind of optional feature and explorers can integrate it or not.
Then, if there is a real feature with those buttons, let's see how bitcoin community react by the way they choose which explorers to use.
Technically, developers can build some kind of algorithm to prevent and minimize potential abuse (but there are always abusements on all systems, no matter how good they are). It is not too difficult to solve like scalability, ie. Next, for potential adverse effects from potential abuse, yes, Tag/ Scam report buttons and Warning textbox are supplements and which have to be supported by further investigation from each user.
Everything has its costs and benefits but if there are outweighting benefits than negative effects, and can help to have a healthier environment for bitcoin (in reality, for the whole cryptocurrency), why not?
Sooner or later, we will see it on most of bitcoin explorers (we already have a third-party site provides that feature) because there are demands there are supplies to bring satisfaction to users. We do have real demands on it, for general healthy bitcoin ecosystem.
