I believe the issue that tilda had with GNOME 3.10 (https://github.com/lanoxx/tilda/issues/29) and that was fixed (worked for me in 3.16) is back in 3.18. Now when I turn on transparency, only two gray dots appear on each side of the terminal. I am using Arch Linux.
Here is a screenshot with transparency ON (notice the two dots in the left and right top corner):
I believe the issue that tilda had with GNOME 3.10 (https://github.com/lanoxx/tilda/issues/29) and that was fixed (worked for me in 3.16) is back in 3.18. Now when I turn on transparency, only two gray dots appear on each side of the terminal. I am using Arch Linux.
Here is a screenshot with transparency ON (notice the two dots in the left and right top corner):