found the mistake!
when i put "content" on a new document...then i prefer to have my text wrapped within a <p> tag.
e.g. typo3 -> if you place content on a new document typo3 automatically renders <p class="bodytext">....modx doesnt do that...so the output is just text without any wrap. (not that good)
now..if i dont format my content the trunc call works....
its not soo good...anyway....i need to think about how to do it better
"(not that good)"
MODx does not alter your HTML (or xHTML preferably). Thats how it was designed and how all of its components were as well. If you want to wrap your content in a p tag, do it in the templates or in the RTE.