Fair question and as one who has modded or owned large forums in my day I'm familiar with the back room. I do understand this side of it from the staff perspective, however being on the other side of it here does offer a different view as well.
For the user, if they have been reprimanded for what they see as the same offense, it's a hard pill to swallow when they aren't given the same courtesy. Past history is obviously considered here and I do think the team tries to look at that where applicable, but at the same time we can't expect a mod to do a deep dive on every person who is reported on.
So yes, it's subjective but at times can feel unfair, other times you know you have it coming and should've known better.