I\'ve looked, but it doesn\'t look like you can apply specific formatting to just comments.
Well, there is an Add-In which will automatically format your comments to a given width (as a side feature).
It is HyperAddIn - the main feature of which is allowing you to create 'hyperlinks' to other places in your code within comments, like this:
// The other half of this logic is in code:ComponentManager.Initialise()
With HyperAddIn installed, the code:ComponentManager.Initialise()
becomes a clickable link.
I have it installed, it works OK, but I must admit that most of the time I don't have the comment formatting switched on.