Complex sentence: The Overactor is often unaware that their tendency to jump on others is often unfunny and more tiresome than the post they are attacking, and often acquires a reputation of being a "whiner".
Split into simpler sentences: The Overactor is often unaware that their tendency to make a show of jumping on others is piteously unfunny, and more tiresome than the post they are attacking. The Overreactor often acquires a reputation of being a "whiner".