Actually, I cant think of a single scene where Imu is raging... Not that I can find one for Sommers either.
My takes arent delusional, I am simply ahead of the curve. As usual, it takes a while but you will end up seeing that I was right.
Gram's ability in Imu's hands = Gram's ability in Sommers' hands.
If anything, it can only be stronger in the hands of Shepperd family because it is a sword of the Shepperd house.
The reason why Zoro isnt fighting Imu is because he is too deadly for him, just like he was too deadly for Kaido and went on to fight someone even tougher.
If old injured Gaban can flatten him with the ground, you dont wanna know what Zoro can do.
Also, I guess another reason why Zoro fights Sommers is because neither Luffy nor Loki could take him out, when he was even weaker.