I posted same question in Joomla forum, but figured I'll try it here too.

I installed cloud module on my site, and want to make cloud tags to be search engine friendly.
On each tag joomla submits following link: http://www.mysite.com/searchword/mytag/

I tried to use following rules in .htaccess files:
RewriteRule ^searchword/(.*)/ index.php?searchword=$1&option=com_search [QSA,NC,L]

This simply does not work - I am getting 404 error.

But, if I'll add R (redirect) flag, then this works:
RewriteRule ^searchword/(.*)/ index.php?searchword=$1&option=com_search [QSA,NC,L,R]

But in this case user can see where he/she was redirected.

Why my redirection without R does not work?
I have OpenSEF installed on my website, but my rules are right after statements:
RewriteEngine On
RewriteBase /

So my rewrite should work, but it does not. Anyone can help me?

Found that OpenSEF was capturing that SearchWord string and thus reporting 404 error. Redirect was forcing to go around OpenSEF.... Solution on how to use this compoent with OpenSEF is posted in my other thread.