Hi diffident,
Did this occur only on the one blog site? And is the RSS feed icon the one on the default page of the blog site?
If open the default page of blog site in SharePoint Designer (SPD), we could find that RSS feed icon was not been defined in master page, instead
it was been defined in the post list web part.
sitefeed.aspx page is not a predefined application page (SharePoint 2007), did it a customize application page?
Your ListViewXML code must been modified. The original code should be like this:
<HTML><![CDATA[/_layouts/listfeed.aspx?List=]]></HTML
But yours has changed listfeed.aspx to sitefeed.aspx.
Please delete ListViewWebPart in SPD > save and open this page with browse > Edit Page > Add a Web Part > select Posts list >
Add it again.
Let me know if there any other questions, thanks.
Best regards. Emir