As your username is linked to your blog I don’t know why this would happen when you reply to a comment on your own blog. Will you please post a link starting with http:// to a comment where you see this happening?
Oh maybe I’ve solved this. But I have to fill in the form to post and I have never done that before. Normally I automatically come up as TBI but this time I had to fill in my email, name and website (and I was logged in)
If you are logged out of wordpress, then you will have to fill in your information. If you are logged into wordpress, then wordpress will fill that information in for you based on your settings under users > my profile and users > personal settings.