Tags have no effect on a piece of text if they simply repeat an existing property of the base text symbol. Generally, this behavior is intuitive; for example, if you have a tag in your text string, but the base text symbol is already bold, then the tag in your string will have no effect. Also, because tags follow the rules of XML, it would be illegal to try and use a tag to 'turn off' the bold property of a base text symbol. Instead, use the tag for this