Display of line/box drawing characters changed in 3.1

• iTerm2 version: 3.1.1
• OS version: macOS 10.12.6
• com.googlecode.iterm2.plist

The white-on-black version on the left is current iTerm, the black-on-white version on the right is from Terminal.app. Both are using Menlo at 24pt. Before upgrading to 3.1, iTerm 3.0.15 rendered the characters in perfect alignment just like Terminal.app. The misalignment is also visible with antialiasing turned off.

This is possibly related to #6049 (closed).

Here's my test data:

╭───┬───╮
│ a │ b │
├───┼───┤
│ c │ d │
╰───┴───╯

Thanks!