Jonathon is not the most optimistic man you will ever meet. Nor is he the easiest to talk to. In fact, Jonathon would have been mind wiped for heresy ages ago were it not for the protection of the Ordo Xenos.
Most space marines find it quite puzzling talking to Jonathon, as they simply cannot understand someone so openly against, seemingly everything, and yet so good at his job. It is assumed that Jonathon is very loyal to the emperor, as despite the fact that he grumbles and complains every step of the way, he has gone well beyond his call to duty, and singlehandedly saved missions and marines alike.
Jonathon did not always work for the inquisition, in fact he was once a fighter pilot for the imperial navy in the Jericho reach, but with his exceptional abilities in flight it was not long before the Watch Master insisted on Jonathon’s recruitment. There has been talk of performing the operations to make a proper marine out of Jonathon, but chapter apothecaries declared that he would be too weak to survive, and Mars refused to assist in any way.
So now Jonathon spends his time providing mission transportation and basic combat exercises flying thunderhawks and the like which Deathwatch tech-marines have graciously altered to work with his smaller size.
Jonathon proudly bares an adimentine skull molded into his flight helmet, as a rare sign of exceptional service under the command of the Deathwatch chapter.