Wesnoth 1.13.12 with 140% font scaling
Windows 7 Pro x64 with 125% font scaling
Monitor 1920x1080
See screenshot:

Some characters could be visible only for half. And it didn't depend is there full screen for game or not.
Known issue, probably a duplicate of #1624?
Font scaling has been disabled for 1.14.
Probably bad decision. New monitors with high resolution would make text smaller and hard to read.
Font scaling is back in 1.15. I tested 1.15.1+dev with Windows 7 scaling of 114% and Wesnoth scaling of 140%.
Let's close it.