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Yes, it is only for the thread replies specifically to his boom thread.

He also give boom upvotes to other user's threads.

Got it. Thanks for the clarification!

I'm glad you did. My pleasure

BOTH !
But you chances maybe are a bit higher when replying to the threads originated by me.

That makes perfect sense. If I can get my sense of timing down, I can participate in more BOOM action. Thanks for your answers and clarifications.