More… in feed

Feed templates are in wp-includes/feed-rss2.php (and similarly named files).

The tag you’ll be looking for is the_content_rss.

I found the template in wp-includes/feed-rss2.php

But how to change the (more…) text there? I cannot find any html with the “more…” string.

Like I said… you’ll be looking for the_content_rss. Follow the link I gave.