Hello,
Yes, you are right, in the PowerShell editor, the percent character (%) is recognized as the beginning of a value reference. To remedy the issue, duplicate percent characters where they are not related to value references. I.e. replace % character with %%. For example, the line you referenced will look as follows:
<table width="100%%" border="0" cellspacing="0" cellpadding="0" style="border-spacing:0;text-align:left;padding:0;margin:0">