In researching Idea Activity Story Missing ContentPeek URL Formatting , I've found that it looks like the Description method of Idea returns the Name instead in version 12.0.1.15778.
Relevant code in Idea Activity Story Default Widget:
<div class="activity-description idea user-defined-markup"> #set($rawBody = $idea.Description) #set($body = $core_v2_language.Truncate($rawBody, 250, "%{ Ellipsis='...', MaintainHtmlFormatting='True' }")) $body #if ($body.Length < $rawBody.Length) <a href="$core_v2_encoding.HtmlAttributeEncode($idea.Url)">$core_v2_language.GetResource('read-more')</a> #end </div>
Even if one prints $rawBody directly without the truncation, only the same string as the name is printed.