Don't rely too much on the warning points. In many instances we haven't even given any official warning points before banning people. You might be in the riskzone of getting banned if you have gotten one or more (usually more) warning/s through PM from a staff member or admin who has told you to stop doing something that's clearly against iwaku's policies and even after the warning/s you continue with your behavior. Everything is judged from a case to case basis, thus it's hard to say which actions usually leads to faster bans, and what leads to getting warning points.
There's a lot of factors that comes into play:
What is the crime?
How serious is the crime?
On how big scale was the crime committed? (How many members were affected)
Did they understand that it was against the rules?
Have we had troubles with this member in the past?
Etc.
If the person has a lot of offences piling up before we catch them, they might only get one warning through PM, and if we see them doing something more soon after having read our warning, it might lead to a ban. Things like smutting with the wrong age group usually leads to a faster banning with fewer second chances than if someone is being a douche (as it is against the law for adults to smut with teens and could get people into serious trouble.)
If it's just minor offences like a too sexual image as avatar or spamming the forum or people's profiles, you will most likely just get some PMs telling you that it's not okay. The only time you might be banned for such things would be if it's either in connection with other crimes or you re-offend even after having gotten tons of warning messages from the staff telling you it isn't okay.
As I said, it is from a case to case basis and depends on the offenses, so some will get a lot of warning points, or just warnings through PMs, while others might get one warning through PM and then they're screwed if they do something again. Warning points are very unreliable no matter if you're looking at other people's profiles (which I'm not certain if you can see) or if you're looking at your own. It's better if you just think about what you might have done that can get you banned and if a staff member has warned you about it already. That's the best indicator that you're in a risk zone. (Though we do send out a lot of warning's without people being in a risk zone. It all depends on what the crime is. Smutting with the wrong age group, you're in the risk zone, having multiple accounts so that you can get into the smut area in the other age group, risk zone. Bump spamming, no risk zone, pervy images, no risk zone.)
So yes, a ban can show up rather unexpectedly, but it's extremely rare that there has been no indications of a ban coming their way. Usually there has been at least one warning through PM beforehand. Usually people get quite a few warnings to better their behavior, and it's mainly when a person has a ton of offenses stacked up, they're doing a criminal act (smutting with the wrong age group.) or might be a danger to our members that we ban them quickly with most likely just one to a couple of warnings through PM.