A character is considered engaged in melee if adjacent to his target.
Point Blank range is 2m or less.
How are you not adjacent to someone at that distance? So, how do you adjudicate whether a target is able to get the PB range bonus? Do people have to be in physical contact, pushing up against each other, to be adjacent?
Why do chainswords have such low penetration? It's not like they do much damage (yes they have tearing). Against even the Inevitable GUards in the starting adventure, a chainsword has to do at least 6 damage to hit (1 point). So unless you have (assuming there are any) a talent that bolsters melee damage, such weapons can quckly become redundant.