Since last update of iTerm2 (3.5.13) and/or Mac OS X (15.4.1), the background color set by escape sequence does not extend to the last column of the window anymore.
This is especially annoying with reverse video, as the text has the same color as the default background, making it effectively invisible in the last column.
To reproduce, run the following commands in zsh or bash shell:
echo $'\e[45m====================================================================================================\e[m'
echo $'\e[7m====================================================================================================\e[m'
I've tried with and without "Hide scrollbars" setting (in Settings : Appearance : Windows), with the same result for both.
See also this screenshot to illustrate this.
Regards,
Tom.