Reproduction steps:
1. Download project "TextIssuesProject.zip" and open in Unity
2. Observe Game view before entering Play mode
3. Enter Play mode

Expected: text size to be the same throughout the scene and line breaks occur (first line in Result.png)
Actual: text is shrunken to fit in one line (second and third lines in Result.png)

Reproduced on: 5.5.5p1; 5.6.4p1; 2017.1.2p2; 2017.2.0f3; 2017.3.0b6; 2018.1.0a1

Note:
the label in the middle with no spaces in its text
the label at the bottom with its text formatted to use zero-width space characters