The swap button of the talk page version is somewhat brocken/misplaced in the MonoBook skin.

The reason is some custom padding we apply to the ..mw-twocolconflict-single-swap-button button via ext.TwoColConflict.Talk.styles.less. This should only be done in skins that use the default OOUI theme (named "WikimediaUI"), but not when the Apex theme is used, like it is in MonoBook.

For comparison, this is how the button should look like. Instead of just removing the padding it might be better to use a more generic or different padding in Apex based skins, so the button is (roughly) scaled to the same size in MonoBook.

Instructions when working on the task:

• Install the Two-Column-Edit-Conflict-Merge extension
• Install and use the MonoBook skin
• Figure what CSS could fix the issue
• Put it into an extra .css file under /modules/SplitTwoColConflict in the Two-Column-Edit-Conflict-Merge extension repo ext.TwoColConflict.Split.monobook.css

If you need help along the way, feel free to poke @WMDE-Fisch