Hi Francisco,
Activity comments within Method are stored as HTML text. This allows users to change the formatting of comments (e.g. font colour & size, text alignment, etc).
The HTML editor used to enter activity comments automatically adds HTML paragraph tags to the text. Behind the scenes, a comment may look like this:
<p>This is a comment</p>
When displaying this, browsers will automatically add space before and after each <p> element. As a result, the activities grid renders comments with additional space before and after the comment, which is why a single line comment appears as 3 lines.
Cheers,
Jonathan