RichEdit
RichEdit1->Lines->Add("тестовая строка");
RichEdit1->SelStart = RichEdit1->SelStart - 1;
RichEdit->SelText
Свойство PlainText = true
RichEdit1->Lines->Add("тестовая строка");
RichEdit1->SelStart = RichEdit1->SelStart - 1;
RichEdit->SelText
Свойство PlainText = true