So, I have a few things that are canon to Chrys and Auri particular timeline, and I took a couple of liberties in terms of sylvari behavior and reaction just for my oc's canon.
Following the trail of "some sylvari feel everything too strongly and get overwhelmed in the Grove", Chrys is one of those types, with the unfortunate side effect of a physical cue when he gets too stressed out. Namely, flowers sprouting in his hair. If the stress gets too out of control, or he tries to force it all down for too long, it makes him physically ill, sometimes coughing up petals and flowers in an attempt to force him into a state requiring medical attention or a few days bedrest in order to recuperate.
Chrys despises the fact that this happens, but it's forced him to learn better stress management as a result, especially since this came to light during HoT where he collapsed in the middle of camp some time into the campaign. Auri, being both his lieutenant and personal mender at that point, chewed him out for letting his stress get that bad.
In terms of reactions, especially in combat, I imagine seasoned sylvari warriors have a subconscious reaction to use whatever means necessary to make sure they can defend themselves. In this, parts of their skin may prick up, so to speak, and coat their bodies in a temporary layer of thorns. Kinda like how a cat fluffs up their fur to seem more intimidating, but these thorns could do very real damage to unsuspecting attackers.
While Auri is more a support type mesmer, they have learned how to reflexively activate these thorns, usually when trying to protect Chrysallus when he's otherwise incapable of defending himself. These thorns require a conscious effort to activate, so if they are untrained or unconscious, then a sylvari wouldn't be able to use their thorns as effectively.
