This is the practice of slapping parentheses around some text and then dropping it into the middle of an existing paragraph.
People usually form paragraphs to deal with a particular rhetorical need. If the new material doesn't meet the rhetorical need, it probably doesn't go there. The parentheses don't change that.
Parabombers are generally not tarred and feathered and run off the internet on a rail, demonstrating the sweet and forgiving nature of wiki-ans in general.
The cool thing about parabombing is that the parentheses make deletion particularly easy. The text to delete is already demarcated by parentheses.