To give each user an access to his web page, I decided in the end to stay with permanent redirections based on regular expressions.
The redirections are set in such a way that the page of a user named "Alexandre Dupont" (fictive name) can be accessed by any combination ending by his name, like
domain.ext/dupont
domain.ext/alexandre-dupont
domain.ext/a.dupont
a.s.o.
RewriteRule ^(.*)dupont$ index.php?id=28&service=viewprofile&username=a_dupont [R=301,L]
RewriteRule ^(.*)pont$ index.php?id=28&service=viewprofile&username=b_pont [R=301,L]
Everything works fine, excepted when the family name of a user is contained inside the family name of another user. Then, the redirection that is applied is always toward the web page of the user with the shortest of the two names. In example above, the redirection is always done toward the web page of user "Pont", even when I type "domain.ext/dupont".
I hoped that the "L" flag would stop applying redirections (as "L" stands for "Last"), but it isn't the case. I also tryied adding the "NC" flag (Non Chain), but without success. Any idea how could I stop any later redirection if the redirection for "dupont" occurs?