Personally i do not have any problems with portraying an image that is more readily acceptable by the general public (or forum members in this case). IF you want to Role play.... great, no problem!!!! BUT......
There are limits.
Things that iMO is acceptable to do...
Adapting to a different personality while online. (you may come accross as this funny humourous person online, while in reality your porclain face will crack and shatter if you try to smile <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />
Leaving out facts about yourself (epsecially those that may cause conflict / make you feel uncomfortable )
Act a character which is purely fictional (and is EASILY recognised for being fictional) E.g. I very often come accross in forums as "goddess of the tide" "Lady of Rain" etc... (IMHO if you really believe that i am the Goddess of the tide.... well then there is not much hope left for humanity)
IMO having vitrual environments, friends, experiences, gee, i have even been virtually married before!!!! (to the prince of thunder) AS LONG as both parties are aware of the TRUE fact here... its all a LIE!!!! none of it is true.
THings that IMO is just a NO GO / TAboo
Deceiving a person in regards to loyalty, trust, reliability etc. (If you say you will / wont do something.... then stick to what you SAID you will / wont do)
Creating false identies (the kind that is realistic and not easily spotted as roleplaying) (You do not change your gender in order to "toy / torment" a person. Nor is it acceptable for a paedophile to enter a chat location under the pretences of being a 14 year old. (In plain english, do not hide your wolf nature in sheepskin!!!!)
Creating events to envoke a response of sympathy, or to turn current events in your favour. (Do not tell people that you were antagonised by Character A to get a response of sympathy from Character B, just because you need Character B to focus on fighting with Character A, while all you actually want to do is make Character C believe that Character B is a very hostile person.... etc)
Do or Say anything that may cause emotional instability / pain to another person.
I think it all can still be summed up in 1 line....
Do unto others what you would like done to yourself!