I have forgiven and been forgiven many many many times.
Especially when behavior only or primarily revolves around game stuff.
When it crosses lines into the individual/personal (such as stalking behavior, doxing behavior, ect) and when it shows a major character flaw (repeated incidences of cheating across many games, repeated incidences of attempting to stir up people against a latest target, or repeated incidences of unwelcome attention/pursuit of people with an unwillingness to hear or pay attention to the word no), then forgiveness becomes a moot point, because regardless of whether I hold affection for that person or if I did at one time, there is just not going to be trust there.
I also dont believe mush people to be uniquely strong grudge holders either. Maybe its just because I have a long history of being extremely involved in community and/or interest group volunteering, but as I have said many times, the worst drama on a mush that I've ever seen does not hold a candle to some of the middle tier drama I saw in the PTA and political orgs, Including territorialism, whisper campaigns, being spiteful to someone's face/behind their back, and even stealing money from people! There are plenty of people with unhealthy behavior problems and obsessions/attachments that glom onto volunteer groups as well. I'd say about the same percentage as mushing really, except for the impact can be a lot worse, because it is face to face, and if you think avoidance of dealing with problematic behavior on a /mush/ is bad...
Like seriously, the year before last year, when a long time much beloved political organizer locally raped a just turned 18 year old /at the state party gathering/, and was promptly removed from all posts/banned from our org, you still had many people loudly complaining about "but he does so much for the party, we cant lose that kind of talent". Sound familiar?
People are people everywhere. Mush people I think tend to be much more on the social/wanting to connect side of things than normal. It is an asset. But does it lead sometimes to hissing and spitting, yes.