This post is starting as a discussion. What did you do 1, 5, 10 or more years ago in games that you regret? What do you still believe is a proper and right decision?
My answer follows:
I started my "modern" MU career in 2010-2011. I had played in the 90s, and a small bit on a Scion game in the aughts, but my real heavy return was on NYC Mush. I played Werewolf and Vampire (and briefly Mage) and staffed as well.
I introduced my ex girlfriend and we played together there, and then briefly on HM, and then for a long fucking time on The Reach.
It doesn't seem that long ago, but when I started on TR, when I began STAFFING, was still in my 20s (barely, I'm 37 now). But I had opinions on games and how to play them. Some of them I feel were right and some I feel may have been misguided.
Strong opinion I now regret? ICA always equals ICC. If you did something that my character felt justified a certain response, I'd respond as such. I engaged in some serious (and not so serious) PVP - from hacking and stalking, to financial warfare, to outright murder (or Torpor, which is often just as bad). I always put my character's decisions front and center, they were the lead character of their own film.
This is, I reflect back, more than a little bit of a dick move. I always say I try to stick as close to Tabletop as possible, and in tabletop, the PCs are the protagonists, the ones who matter. On a MU, every PC presumably matters to the person playing them. I didn't consider their OOC feelings, usually. It was OOCly to me "just business".
tl;dr on that front I was a dick to you, probably. My B.
A strong opinion I still hold, is that a game needs to stick to the fucking theme of whatever game it is meant to be. If you are a Chronicles of Darkness game, you should either reflect the books, or mak eit clear what you are doing. Tone should be, while not consistent and omnipresent in every scene, reinforced and supported. Significant departures from established lore, such as Pure-Forsaken handholding, or Vampire's being completely nice and sweet and just humans with cool goth powers, should either be frowned upon and removed, or else reflected in the game's specific lore and story. Don't punish a player for playing the game you advertise to be playing.