Bear with me here. Because I have. Some thoughts.
First things first, visit here for another in depth analysis of the table carvings that doesn’t really have anything to do with my commentary, but I found it while looking for the picture for the table and liked their analysis. So….
Anyway, the table. We watch as Sam and Dean carve their own initials, and we know Mary’s initials get added after her death in season 14. That’s all fine and dandy. And we know Cas and Jack’s names get added sometime after Cas’s death, and presumably after Jack leaves, but we don’t really know when, or even by who. We also don’t really know who carved Mary’s initials, not really.
However, we see Sam and Dean’s different styles of carving into things twice. (Sorry about the gore it was the cleanest picture I could find of the car initials completely.)
Now, neither of the boys are identical, however, we can see a distinct difference between Sam and Dean’s style. Dean carves deep, so it will stay a long time, despite wear and tear. Sam however carves wide. He carves out his initials instead of making a hole. It’s much more surface level, almost as if he’s scared of getting in trouble and wants it to be easier to get rid of. But that’s something we can get into later.
When they add Mary’s initials there are a couple things that tip us off that it was Dean who actually carved them in, A) they’re from that direction, which is the side/seat Dean almost always sits in when both brothers are up and about. And B) it has that same depth to it as his initials, and the same style of how the lines meet. Therefore Dean carved Mary’s initials.
However, this brings us back to Jack and Cas.
Both Cas and Jack’s names have that same width over depth, more surface level carving as Sam’s initials. Especially when compared to Dean and Mary’s. The S in Castiel has very similar strokes to the S for Sam’s initials, and the A’s and C’s in their names are similar if not the same (or as same as they can be considering they were carved into wood and sometimes the grain of the wood disrupts flow a little bit).
This, to me, means that Sam was the one to carve Castiel and Jack’s names into the table. And I’d even bet, that he didn’t do it until after Dean died.
Now I could be wrong about this last part, but if I’m remembering correctly, we don’t see all five names/initials until after Dean’s death. While Sam is sitting at the table (notably in Dean’s spot, and wearing dean’s sweatshirt.) with Miracle, so it’s plausible, and even probable.
And I’d bet he did it when he decided he couldn’t live in the bunker anymore without Dean because every little thing reminded him of his brother. And I’ll bet he did it because they are a part of his family and they deserved to be remembered too.
Castiel, the angel of Thursday, the angel who betrayed heaven for the sake of humanity. Who chose over and over again to take the Winchester’s side over any other supernatural being because he trusted their sense of right versus wrong. Castiel, one of the Winchester’s only friends who stuck around, who made sure that they took care of themselves, and made sure to save them while they were saving the world. Castiel, the Winchester’s best friend.
And Jack, their kid. Sure, he was the spawn of Lucifer, but he was Castiel’s kid. He was Sam’s kid, and he was Dean’s kid. (I’ll get to a rant about Dean and Jack’s relationship at a different point because I have thoughts.) Jack saved the world, and he turned out good because of Castiel, because of Sam, and because of Dean. Jack took the mantle of God to protect the world, so he could protect his family, and keep the angels from interfering with human affairs.
