Comment 1 for bug 1622397

Pantheon-terminal uses the vte widget for terminal emulation, and vte most definitely does _not_ do such distortion. It's probably your window manager that does it. Check your wm's settings to see if you can disable this.

One thing, though: vte rewraps its contents which is a relatively expensive operation (depending on the scrollback size) and only repaints its area once it's done. This can lead to the distorted letters being displayed for a longer time. See if disabling rewrap (not sure if pantheon-terminal lets you do that) or decreasing the scrollback buffer size shortens this period.