MR discussion subpixel heights cause unexpected behavior

What's the observed behavior?

On Chrome, when viewing this comment https://gitlab.com/gitlab-org/gl-vue-cli/merge_requests/1#note_116994290 the reply box is missing a border bottom (sometimes):

Why does this happen?

This issue happens because Chrome rounds down sub-pixel values for table displays. Screenshot (see how the surrounding tr rounds 1182.48px down to 1182px):

See https://gitlab.com/gitlab-org/gitlab-ce/issues/53973#note_167540725 for more details.

Expected behavior

No subpixel heights should be generated. As observed, this can cause unexpected browser issues.