Personally, I think Quesadilla raises some valid points. I think it demonstrates that there are many types of punter. To oversimplify though, we might say that there is the view as expressed by Quesadilla in this thread and the views as expressed by many of the married/attached members in this same thread. There seem to be however, definitely more posters on this site who fall into the second camp of punting while married/attached.
Everyone starts somewhere with this particular pastime and to begin with, will have no point of reference at all. I certainly don't talk about punting with my friends. Maybe a single newbie gets into this hobby, sees this site or something similar and comes to regard option 2 as a lifestyle inevitability that everybody does. He then finds himself in a relationship, has a punt and feels like shit afterwards because he hasn't given enough thought to how this fits with his own moral code. So it is good to see the other opinion being put forward.
About 4 or 5 years ago, my then girlfriend lived a two hour drive away and I didn't see her as often as I would have liked. I got totally pissed at the pub one Friday night and in my drunkenness decided an impromptu restart to my punting career was a great idea. I soon regretted it and my own personal guilt more or less finished the relationship within the next few months, though I never told my ex and she never found out. I learnt that the whole deception thing was something I personally cannot deal with and that it was better for me to keep this as a hobby for when I'm single. I know there must be many more with similar thoughts who just don't post. Having read some of the married posts on this site in general though, I do acknowledge that some of the situations described do sound very difficult indeed.
I am not judging anybody and have been happy to take on board the knowledge of all kinds of punter on this site and am happy to share what little knowledge I have regardless of anyone's opinions. I have been in situations where I knew someone who was cheating on their partner and I have never intervened because I took the view that it was not my place to get involved. Really I am just saying that if you break your own moral code, you will feel like shit, I am not trying to argue for a specific moral point.