Expand truncated table cell content on hover

I'm working on a project using Google's Material Design and am running into an issue where we need to truncate table cell content. There is a spec for truncating table headers and showing the full label on hover, but nothing about table content. The content I'm looking to truncate is not primary for the user (field for comments about entry), but they may want to see it.

• Is truncating and showing cell content an acceptable pattern?
• If so, should the entire row expand down, or just the cell expand over other content?