CB user link in event registration

I agree with you; I think this is a typical issue with the Joomla router, not JEM. Possibly, if the user creates a menu for the CD user profile, it might work.

That is the probleem. I do have a menu item for the profile. 
And links in CB do open the correct URL/[username] but the link in JEM plug-in doesn’t.

To overcome this problem, can’t I change the standaard url in plug-in php to use a real url as it is in the webpage. This is quick and dirty but of it works, we dan go live with the new webpage 

I'm glad the trick worked for you, that's how the Joomla router works.
Sorry but If I don't see the issue (simulate in localhost), I can't debug it.
Feel free to modify the plugin and suggest improvements or any other idea about it.

I have the Same issue and the problem it causes is, that with the wrong link the modules from the frontpage are loaded (search, latest news, events) before the profile view is showing.

Sorry, I don't understand. Can you specify, please.

Normally, when I click on the link to a user profile, a defined menu item is opened, to which special modules are assigned. In my particular case, there are also a few template adjustments that result from the CSS class of the menu item.

However, if I now open a profile link from the participant list, it acts as if the start page is opened and the modules that are exclusively assigned to the start page are loaded with the profile.