[Foundation-l] Is it possible to spoof an IP in the change log?

[reason]

Hello,

A couple of users on my wiki have been arguing, and it appears that one
of them has resorted to vandalizing the other person's Wikipedia page.
This suspected vandal always accesses my wiki from the same IP, and that
IP was associated with sexual comments that were added to the other
user's Wikipedia page. 

I'd just like to know if this is good evidence of misconduct, of if a
savvy user could spoof someone else's IP address and frame them for
misconduct.

Thanks,
AdamRetchless