My condolences on the untimely demise of your friend. Someone I knew (not very close) did that on his 30-th birthday. Left a small child behind and a hand written note. To be honest, if we were close friends and he left a comment in my journal, I'd be devastated. My heart is going to you and your friends.
So, yes, there may be life events where logged IPs will become useful and aid in police investigation.