It seems like your current template injected those duplicate field into Easydiscuss, if I switch to Joomla default Protostar template, it will show correctly, you can check my attached screenshot below.

Can you consult with your template provider regarding this and see how it goes?

I see,
for now I solved by adding thse 2 lines to my custom css file.
My template is Rockettheme Galatea in case someone stumble upon the same issue.

#ed .chzn-container-multi .chzn-choices {display: none}

#ed .ed-filter-bar .chzn-container-single .chzn-single {display: none}

As far as I see this solution does not affect other elements around the site and solves the issue.

Thanks

Thanks for updating us on this Niccolo.