Compiling tig (from master) with libncurses-dev but no libncursesw5-dev installed causes tig to experience some alignment issues and repaint problems that do not happen with libncursesw5-dev installed/used instead.

Here's how it looks with the following configuration:

...
configure: WARNING: The found ncurses library does not support wide-char.
configure: WARNING: This means that tig will not correctly render UTF-8.
...

giving

tig version 2.5.7
ncursesw version 6.1.20180127 # this is wrong?
readline version 7.0
PCRE2 version 10.31 2018-02-12

And here's how it looks compiled with libncursesw5-dev correctly installed instead:

tig version 2.5.7
ncursesw version 6.1.20180127
readline version 7.0
PCRE2 version 10.31 2018-02-12

Behavior observed under both Kitty and conhost (Windows cmd). Behavior not reproducible in some other terminal emulators.

I don't think UTF-8 is a factor, at least it shouldn't be as I don't think I see any non-ASCII characters in the output on screen at a glance. If tig is using Unicode/non-ASCII symbols for display/formatting, then it shouldn't if no libncursesw was detected (in which case wide character support would only be used for git messages or file contents containing Unicode characters).