Silksong has consumed my life

Actually, the reason is mainly because of this amazing comic by @localaceken, where I got the idea to start drawing him with a beard because it fit him well in DR.

As for why a beard with no mustache? Uh, I don't know, I think it was the easiest to draw, since I had a lot of trouble drawing beards at first. The design of adult Aang may have been unconsciously influenced, but I also paid a little attention to what Future Jay looked like and think his beard like that.

Personally, I really like the idea of ​​Jay growing a beard post-merge for several reasons. First, it's actually the easiest way to age his design, and it makes a noticeable difference between him and pre-merge Jay (I like to joke that he actually did it to look older lol).

And also because, being Jay, I imagine him wanting a change of image, just like he did with Rogue later on by growing his hair out. Whether it's to distance himself from his past, or to feel more comfortable in a body that doesn't feel like his own, I like to add these little details that show how much time has passed since the merge. I also think there's some irony in having Jay increasingly resemble his future self (later getting the iconic eyepatch) while simultaneously seeming to move further away from that destiny.

And the final answer: he looks hotter with beard.