I don't even know why that's technically against the rules (though I can obviously see how it would be abused), since if a person creates a thread they might want to reply to other members' posts, even if that means making multiple posts within a 24-hour period--and I do realize you said as much in the part of your post that I snipped out.
For one, repeated bumps of the same thread are very annoying to users who are watching the thread or the board, or just look for new stuff on the board. This is not twitter, I don't need my phone buzzing incessantly with one-sentence replies from the same person. That reason alone is good enough for me to report any consecutive posts without wasting my time trying to guess the intent of the poster.