In Chapter 1018, Who’s Who clarified that his anger is not necessarily directed towards Luffy for him eating the Gum-Gum Fruit, which would imply importance to the fruit unrevealed throughout the story, but instead his anger is directed towards Shanks.
I’ve been speculating since Chapter 1017, that Who’s Who was imprisoned for a reason beyond the Gomu Gomu No Mi being stolen. What would make the World Government imprison such a significant figure in their CP9 organization? I think Shanks status as a Celestial Dragon could fill the gap. Who’s Who was vague and said he made a “single little mistake” which I speculate could be attacking Shanks or more specifically trying to defend the ship he was guarding from Shanks, which is not allowed.
I think evidence of this can be seen from Marineford. While much credit is given to Shanks as a diplomat and someone reasonable the World Government can work with, I believe the behavior by the Admirals suggests they may not be allowed to attack Shanks. This panel shows the light response letting “Dragon’s son escape” warranted from Sakazuki, essentially throwing his hands up and saying “Blast you!”
After Luffy escapes and Shanks arrives, the Admirals give up, which is kinda crazy in retrospect.
Sengoku goes as far to tell Shanks he will accept full responsibility for ending the war. I think these could be breadcrumbs of behavior by the World Government that doesn’t make much sense without considering great status from Shanks. While we’ve assumed that is because of his personality and level-headedness, a fantastic twist would be revealing that the World Government was compelled to follow him because they serve Celestial Dragons.
Shanks being a Celestial Dragon would also inform why the Gorosei were willing to meet with him. Perhaps the “pirate I need to talk to you about” was Who’s Who because he is an escaped, powerful person with knowledge of Shanks’s status as a Celestial Dragon.
This could be evidenced by CP0 in Chapter 1018 only caring about Who’s Who’s death, something they might directly do serving a Celestial Dragon. It could be Shanks met with the Gorosei and wanted them to kill Who’s Who, and so they sent CP0 to Wano. More breadcrumbs.
Finally, thinking long-term, it would be one of the greatest twists for Oda to reveal Shanks as a Celestial Dragon and it would give impetus for Luffy and the Straw Hats to fight Shanks. Luffy has made clear multiple times that he has plans to “crush all four emperors” “as long as Shanks isn’t first”.
In Wano, Luffy told Hyogoro he’s gotta “beat em all” and earlier told Fujitora that he’ll “never become King of the Pirates” unless he beats “each and every” emperor”.
I really think it fits. This is not considering some of the other speculations, like connections to God Valley and Roger. I think Chapter 1018 might add support for Shanks being a Celestial Dragon.
*Theory by gregbraaa