We do not have any registration system in EasyDiscuss. It falls back to the registration in Joomla.

Thanks mark, any recommendation for a simple (and compatible) registration component with custom fields adding possibility ?

Since you have EasySocial installed, why don't use EasySocial?

This is an intern QA website where we want to use ED only to have the lightest structure !

The ED profiles looks simple and awesome, we'll consider using joomla only if we cant find a simple registration component ..

I suggest sticking with Joomla's registration if lightweight is what you want

Thanks Mark !

Actually we are using the guest posting feature (name + email) for quick questions, i guess they will receive email notifications if they have responses ?

Yes