You try to break a line in the e-mail editor using 'enter' key of the keyboard but a extra line divides the text.
Reproducing the Issue
1) Go to Service work center
2) Select Templates view
3) Open an e-mail channel type template
4) Edit the template in the pertinent pane
5) Hit 'enter' key in a line and notice the extra line put in the text
This is the current behavior of the system.
You can use, as workaround, the combination 'shift+enter' for achieving a single line break. Please note that in Silverlight UI (where HTML tags are visible) the use of <br> tag can be evaluated for these needs.
KBA , SRD-CC , Cross Components , How To