It think is that he was jealous so unferth tries to undermine him unjustly.
There is an envelope marked with the instructions that it is not to be opened until the death or disappearance of Dr. Jekyll. This implies that Dr. Lanyon knew something secret, but was unwilling to reveal it at first. He waited until there was no more "hope" of Dr. Jekyll staying normal.
I think he means that humans don’t like being alone. It’s our nature to find someone or have a companion throughout our lives. We instinctfully talk to people to interact or make friends. That’s what I think he means
