Why does htaccess RewriteCond ban all pages after the characters in the file?

Question

CodeIgniter

Hi people!
the essence of the problem, I have an htaccess file that contains:
RewriteEngine on
RewriteCond $1 !^(index\.php|i|robots\.txt)
RewriteRule ^(.*)$ /index.php/$1 [L]
and I have dynamic linking inside the framework.
those. domain.com/$username
where $username is set by the user himself during registration,
but here's an interesting jamb I found.
Since in htaccess we have a rule for |i|
then all users whose name starts with i* will not be able to get to the page, since they will be redirected via htaccess to the /i*/ folder that does not exist on the server,
respectively, in the config I have
$route['(:any)'] = 'user/index/$1';
How can this be fixed? Thanks in advance
codeigniter 2.2 framework

Answer 1

Question removed
Solution:
RewriteEngine on
RewriteCond $1 !^(index\.php|robots\.txt)
RewriteCond %{REQUEST_URI} !^/i/
RewriteRule ^(.*)$ /index.php/$1 [L]