So you have tags around all the content saying what language it's in, and only the correct language should be displayed?
I can't see why there would be blank space, your code looks correct to me. Do you have a demo website where I can see it running?
Unfortunately the wiki is running local at the moment.
This is the wikitext I want to display, depending on the language-setting.
This is displayed every time.
<section lan=lux>Only luxembourgian language.</section> <section lan=en>Only english language.</section> <section lan=de>Only german language.</section> <section lan=de>Only german language.</section> <section lan=en>Only english language.</section>
<section lan=lux>Only luxembourgian language.</section> <section lan=en>Only english language.</section> <section lan=de>Only german language.</section> <section lan=de>Only german language.</section> <section lan=en>Only english language.</section>
This is displayed every time.
<section lan=de>Only german language.</section> <section lan=de>Only german language.</section> <section lan=en>Only english language.</section> <section lan=de>Only german language.</section>
If luxembourgian language is setted up, just the first and fifth line are displayed. But there's a lot of space between the first and fifth line, between the fifth line and the second line without tag, and afterward this line.