I can only guess. But I did receive a confirmation email about my avatar being taken down due to their policy; and the appeal message mentions "misrepresenting my identity".
That doesn't really follow. Especially since they specifically said the avator is the issue:
>they removed my avatar for not complying with the TOS.
Though unclear how OP is talking about both avatar removal AND account ban? Feels like perhaps half the story.
How they got from avatar issue to a whole account ban I can't tell you but I'd imagine there is something in the ToS that makes it viable (impersonation etc).
Not saying it's fair ofc...but plausible
Timeline:
Day 1: Account is restricted/blocked, on login I'm presented with ID verification and a "we'll let you know".
Day 2: I receive an email as a follow up to the ID verification. "Your appeal has been denied and your account will remain restricted". No reason given beyond having "misrepresented my identity".
Day 2.5: Slightly later, I receive an email saying my avatar has been removed because it didn't comply with the TOS and I should upload a real photo.
"Your profile photo may be removed by LinkedIn if it doesn’t comply"
According to this, the reason they were banned is not due to their avatar (but we can't know because LinkedIn has declined to elaborate, according to the OP).