They're not special chess terms like initiative, breakthrough, and blockade are. To know how the person was using them it would help to see the position.
But of course we can guess. A diversion is probably a short lived initiative used to gain tempi or arrange your pieces more favorably before the opponent takes the initiative back.
A blind offensive would probably be an attacking sequence that doesn't take time to meet any counter threats made by the opponent.
What is a "diversion" or "blind offensive?" Where can I get more info? I tried to search the Internet and Chess.com with no results.