I do not quite know if this is the correct place for this message so please excuse me if it is not.
I appreciate the hard work the admins put in to keep the ArchWiki clean but I think that there is a case to include the edit about swapping mouse buttons on the Xmodmap page.
I was looking at matters from the perspective of a new user (1 in 9 of whom will be left-handed) who just wants to quickly see how to swap buttons. I took a careful look at at the Mouse_buttons#xmodmap_tweaking section which you kindly included in your comment but could not find an explicit reference on how to do this (though it does contain more detail like you said).
The edit was meant to be in the same kind of mind-set as the section immediately preceding - Xmodmap#Reverse_scrolling. This also is not explicitly described in the Mouse_buttons#xmodmap_tweaking section but seems to fit in well here.
I appreciate being relatively new to contributing to the Wiki and it takes a litte time to get used to things but I think there may be a case for this.