Having a small display or plugins that add additional columns to the Pull Requests page for a repo cause the Summary column to be truncated. 

Often for users the Summary column is the only one they care about when finding a PR to review. As a result, this causes unnecessary friction for users trying to find the PR that they need to review. Our users spend a lot of time reviewing PRs, so the extra clicks to find the right one add up a lot over the course of a day.