I found another account with the same problem.

For these accounts, the username has some alphabets with some accents. Is that a reason?

EDIT: When I remove those alphabets having accented characters, it works fine.

I found an trac ticket for this issue. But in a differenet scenario.

http://trac.elgg.org/ticket/4173

Elgg.1.7.8 works ok
Elgg 1.8.1 does not work
I tried stephanmüller

http://community.elgg.org/pg/forum/topic/824833/german-umlaut/

we're duplicating topics ?

@DDS:

Thanks for testing. So its confirmed that its a bug in 1.8.

These two posts are completely different. This thread is about hyperlinking of incorrect URL when the username has a accented alphabet.

The issue mentioned by Helmet is not clear to me. I do not get "Forbidden" error.

What do you get ?

I got 403 with same name as your site in 1.8 

DhrupDeScoop
18 minutes ago

Elgg.1.7.8 works ok 
Elgg 1.8.1 does not work 
I tried stephanmüller

Both problems must be conected -- b/c I belive they relate to ==>

chr escape(chr) encodeURI(chr) encodeURIComponent(chr)
ü     %FC          %C3%BC            %C3%BC

I do not have much information about the encodeURI. If you have said, it should be then. :)

I tested that in a differenet setup in my office. so I did not try what will be the actual error page.

My area of interest was that the incorrect hyperlink url in the "New Members" section in the index page and in the "Edit Profile" and "Edit Avatar" links for such special username accounts.

I have the same problem that the strange linking was appear when i use japanese charactors(utf-8) as username. so i think there is the problem  on encoding as @DhrupDeScoop said.

I think I traced the cause of this ;-)
it is the badly formed Link
http://elgg1810.hackersgalaxy.com/http://elgg1810.hackersgalaxy.com/profile/stephanm%C3%BCller
Notice the duplicatin of the http://xxx ? 2 x   ??
So - of course - that is a 403 Forbidden ;-P 
Means - the non-English chars in the UserID
is being screwed by the Elgg Core code somewhere.. inside there.
Can see ? why I am called 'The Scoop' ;-)
I might look for that fuNnI code sometime..
Gotta eat sumthing and take my Meds first LOLZ ;-P !! 

The ticket for this is http://trac.elgg.org/ticket/4190

Plan is to fix for 1.8.2 release