When multiple instances of the mod_comments (v4) in the "Most Commented" mode are published on the same page, selecting different sections from the drop down list does not work as all instances seem to have the same section (although in their setting they all have different sections).

Workaround: this module also has an input box for multiple sections so just insert the section(s) ID(s) there (while also having a section selected in the drop down list).