Yes, you can change your user name twice a year. You may post it in the thread or PM it to a moderator. Once the name is changed expect a site email that you will need to act on to reactivate the account. Duplicate names are not permitted so use the Members link in the upper right hand corner of the page to check if the name you want is used. To the system you are a number and every occurrence of your name other than a text block will be changed to the new name. All posts and replies will remain linked to your account.
