How to reproduce:
1. Open the attached project
2. Open the "scene" scene
3. Select "New Text" from the Hierarchy
4. Set the "Character Size" to 1 in the Text Mesh settings
5. Set the "Font Size" to 500, notice the pixels near letters

Actual result: Pixels are generated near letters. (Screenshots "1.png" and "2.png" attached)

Note: The pixels location is changing depending on the "Font Size".
Note: The pixels are not generated when "Character Size" is 2 or higher.

Reproducible with: 5.6.4p2, 2017.1.2p3, 2017.2.0p1, 2017.3.0b9, 2018.1.0a4.