I'm Australian and would not hesitate to call myself a "pedantic wanker" in public (because, well... I often am!).
There is a very small chance that someone (most likely elderly or particularly conservative) may be offended. IMO though, it's quite socially acceptable, and unless you are in a particularly formal setting, the risk of it being considered offensive is extremely low.
However, I work with a lot of people, from all over the world. Whilst my colleagues know me and have learned the context of my speech patterns, I also realise that the casual Australian vernacular can be a little harsh for those that are unaccustomed.
I'm pretty casual by nature and wish to be authentic. So I am looking for something that is not too formal or contrite and maintains a sense of playfulness. I.e. I'm denigrating myself, but mainly as a tool to soften the impact of my critique of someone else, rather than seriously putting myself down. So I'm looking for something that I could say in a similar tongue in cheek way.
Explicitly, I'm wondering how I would best rephrase a sentence such as "I just wanted to be the pedantic wanker and point that out!" [that = a mistake you made that doesn't really matter].