In some parts of the UK wanker is used as a term of endearment.
i.e. You really should learn to spell properly, you wanker.
Actually means "If you wish I could point you in the direction of an online dictionary to assist you with any future posts you may make, friend."
or
Another example of how confusion may arise when in conversation with folk that reside in certain areas of the United Kingdom would be:
You only think it's an insult, you wanker ?
Anyone using the above is not doubting your intelligence - they are merely looking to help clarify your understanding of the situation.
Should a similar occurrence happen here on the main forums then the use of a graphic can say more than any amount of words. Something akin to the following would probably have saved myself typing anything in this reply:
;-)