That’s by design. If there is html in the text, Wisej will not convert CRLF to <br/> since it assumes that the text is html and the developer wants to decide the formatting of the text. If there is no html in the text then CRLF are converted to <br/>.
Otherwise you’d be forced to put html in one single line and have no control over the line breaks.
If you don’t use </br> it works all right. Now try
var testMessage = “Line 1 NL” + Environment.NewLine + “Line 2 BR</br>” + “Line 3”;
and you’ll see Line 1 and Line 2 on the same line.