You can disable the Reputation system for your account. This way, any reputation which you do get will be neither known to you nor to others.
I do not think that you can purge the reputation from your system, however, without asking a moderator to adjust the number for you. And I don't know why you would want them to do it this way, either. I think the first way should be good enough for what you want.
If people want to thank you for your posts, it will generate positive reputation. If you don't like this, ... I don't know what can be done about that.
