The OP, having asked his question courteously, is entitled to courtesy in return. Perhaps he simply wants an answer to his question.
The word "bump" is used when a poster e.g posts what he thinks is a provocative question, or makes an intriguing comment, which he hopes and expects will lead to further discussion -- but then nobody answers.
His question has fallen on deaf ears, with a dull thud.
So, after e.g a day of silence, he types "bump", as his comment on the dull thud. It means, "C'mon, isn't anyone going to take me up on this?"
