About Showing/Hiding formatting tags
You can set the Formatting display style option in the Options dialog box to show or hide commonly recognized tags, such as bold and italics, for example.
By default, SDL Trados Studio settings specify that recognized formatting tags are hidden, therefore when you insert commonly used tags from the QuickInsert group or by another method, the tags remain hidden and instead the text is formatted in the style in the in the Editor window. For example, text that is tagged as bold is displayed in bold with no tags.
Commonly used formatting tags will also remain hidden even when you change how tags are displayed from the different options he View tab > Options group in the Editor view.