To

Do this

Insert text

Right-click the block to enter text-entry mode. Right-click again to exit text-entry mode.

Copy-Paste text

You can copy text from other applications into a comment block by pressing CTRL+C to copy the text and CTRL+V to paste it.

To retain formatting, activate Use Rich Text Format in the Edit Preferences dialog. This allows Greek letters and math symbols to be mixed with regular fonts. When Use Rich Text Format is not activated, text reverts to the format specified in the Fonts dialog.  

Resize block

Drag on its edges.