Problem:
When 'ignorecase' is set, the default keymap Q and Q would exit visual
mode.
This issue was raised in #28287 and a fix was applied in #28289.
However, `==` operator is subject to user `ignorecase` setting.
Solution:
Switching to `==#` operator would guarantee case sensitive comparison
between visual mode and linewise visual mode.
Co-authored-by: Kuanju Chen <kuanju.chen@mksinst.com>