First, for simple tag formatting, I'd use the TRichEdit component. But as you wish to disable formatting, I don't know why you simply don't use the TMemo component. By the way: When using the TRichEdit component, you have a property called: PlainText. Make use of it, if you definitly need a TRichEdit (with formatting support).
Dankeee denniss you are awesome , you delphi god