Hi NIna,
The rss feed is actually will shows same as your frontpage listing view. If you have make truncation(
http://take.ms/sopZA )/ add readmore tag in the blog post in will shows as the frontpage listing.
I haven't been able to locate the function that creates the rss feed
Basically it will go into the execute function in the file:
/administrator/components/com_easyblog/includes/formatter/types/feeds.php
where there is a checking where if you choose fulltext or introtext in the line 78 onward
http://take.ms/Nqlr7
Where it post was get from the file:
.../administrator/components/com_easyblog/includes/post/post.php
function getContent/getIntro according to the setting you've set in the backend.