[lynx13]

Okay, I think I solved it myself.

The working code is as follows:

# BEGIN bbPress



#Options +MultiViews



<IfModule mod_rewrite.c>

RewriteEngine On

RewriteBase /forum/



RewriteRule ^page/([0-9]+)/?$ /forum/index.php?page=$1 [L,QSA]

RewriteRule ^forum/([^/]+)/page/([0-9]+)/?$ /forum/forum.php?id=$1&page=$2 [L,QSA]

RewriteRule ^forum/([^/]+)/?$ /forum/forum.php?id=$1 [L,QSA]

RewriteRule ^forum/?$ /forum/ [R=302,L,QSA]

RewriteRule ^topic/([^/]+)/page/([0-9]+)/?$ /forum/topic.php?id=$1&page=$2 [L,QSA]

RewriteRule ^topic/([^/]+)/?$ /forum/topic.php?id=$1 [L,QSA]

RewriteRule ^topic/?$ /forum/ [R=302,L,QSA]

RewriteRule ^tags/([^/]+)/page/([0-9]+)/?$ /forum/tags.php?tag=$1&page=$2 [L,QSA]

RewriteRule ^tags/([^/]+)/?$ /forum/tags.php?tag=$1 [L,QSA]

RewriteRule ^tags/?$ /forum/tags.php [L,QSA]

RewriteRule ^profile/([^/]+)/page/([0-9]+)/?$ /forum/profile.php?id=$1&page=$2 [L,QSA]

RewriteRule ^profile/([^/]+)/([^/]+)/?$ /forum/profile.php?id=$1&tab=$2 [L,QSA]

RewriteRule ^profile/([^/]+)/([^/]+)/page/([0-9]+)/?$ /forum/profile.php?id=$1&tab=$2&page=$3 [L,QSA]

RewriteRule ^profile/([^/]+)/?$ /forum/profile.php?id=$1 [L,QSA]

RewriteRule ^profile/?$ /forum/profile.php [L,QSA]

RewriteRule ^view/([^/]+)/page/([0-9]+)/?$ /forum/view.php?view=$1&page=$2 [L,QSA]

RewriteRule ^view/([^/]+)/?$ /forum/view.php?view=$1 [L,QSA]

RewriteRule ^rss/?$ /forum/rss.php [L,QSA]

RewriteRule ^rss/topics/?$ /forum/rss.php?topics=1 [L,QSA]

RewriteRule ^rss/forum/([^/]+)/?$ /forum/rss.php?forum=$1 [L,QSA]

RewriteRule ^rss/forum/([^/]+)/topics/?$ /forum/rss.php?forum=$1&topics=1 [L,QSA]

RewriteRule ^rss/topic/([^/]+)/?$ /forum/rss.php?topic=$1 [L,QSA]

RewriteRule ^rss/tags/([^/]+)/?$ /forum/rss.php?tag=$1 [L,QSA]

RewriteRule ^rss/tags/([^/]+)/topics/?$ /forum/rss.php?tag=$1&topics=1 [L,QSA]

RewriteRule ^rss/profile/([^/]+)/?$ /forum/rss.php?profile=$1 [L,QSA]

RewriteRule ^rss/view/([^/]+)/?$ /forum/rss.php?view=$1 [L,QSA]

RewriteCond %{REQUEST_FILENAME} !-f

RewriteCond %{REQUEST_FILENAME} !-d

RewriteRule ^.*$ /forum/index.php [L]

</IfModule>



# END bbPress

As you can see, I commented the Options +MultiViews out and let the bbpress-generated .htaccess do the rest.

I was just lucky and experimenting with different .htaccess in this subfolder for hours.

Thanks anyway!