Imagine I write an article with quoting some author. The bot copies the text, and searches for a source. Text matches the source, it then flags my post.

There is no definitive way to prevent unfair flagging since there are countably infinite ways to reference a source.

So you'd also be flagging for a sort of referencing you don't approve.

Another point is how does the bot prove uniqueness? Let's say I copied some text from an article I wrote, but my name on STEEM isn't revealed, I have to get flagged or dox myself?

I think the bot should only look for text on google, then comment a potential plagiarised source.

Downvotes will dictate whether or not the bot was accurate.