Original problem was that join competition button was under wrong heading and added users were under wrong heading as the MediaWiki pages html structure was changed. This is fixed now, but there is still need to test if the gadget works with different UI settings.
Current expected status is that gadget works with Vector 2010 and Vector 2022 with default settings, but it is not tested if it will break when settings are changed. It doesn't work with other skins.
Gadget
Test
[x ] Vector 2010 works with different discussion tools settings in editing settings tab
[x ] Vector 2022 works with different discussion tools settings in editing settings tab