This is what was in discussion
I did some extensive testing, and here is what I found:
Header - works in category & thread display, not in forum display
Above Content - works in category & thread display, not in forum display
Above Top Breadcrumb - works in category & thread display, not in forum display
Below Content - works in category & thread display, not in forum display
Above Bottom Breadcrumb - doesn't seem to work at all
merc_position_22 - main page - appears below sidebar, all others - above bottom breadcrumb. With page criteria enabled; works in category & thread display, not in forum display
Below Bottom Breadcrumb - works in category & thread display, not in forum display
merc_position_24 - doesn't seem to work at all
After Everything - works in category & thread display, not in forum display
Above Thread Messages - works
Below Thread Messages - works
Before Quick Reply - doesn't seem to work at all
merc_position_20 - works in thread display only
merc_position_21 - not at all
After Quick Reply - works
Message Body - don't see where it posts at all
Below Message - doesn't work