The Page Previews feature shows a line break that is not shown in the article where some templates are used. Examples can be found here, listed with the template used.
Description
Description
Event Timeline
Comment Actions
Indeed, The extract_html value of https://nn.wikipedia.org/api/rest_v1/page/summary/Ragnar_Frisch is
<p><b>Ragnar Anton Kittil Frisch</b></p>\n<pre>var ein nyskapande norsk økonom. </pre>
Comment Actions
The problem also occurs in Visual editor mode. It could be related to the use of brackets in the template, as a similar template where brackets are added manually (Mal:Datoar) does not get the unwanted linebreak and pre-formatting. It does, however, get an unexpected space added after it.
Comment Actions
Same happens in Parsoid: https://nn.wikipedia.org/api/rest_v1/page/html/Ragnar_Frisch.
https://nn.wikipedia.org/w/index.php?title=Mal:Levde&action=edit has a </pre> but no <pre>.