Easy enough with a macro e.g.
Code:
Sub ReplaceComments()
Dim oComment As Comment
For Each oComment In ActiveDocument.Comments
oComment.Scope.Font.Underline = wdUnderlineSingle
oComment.Scope.Font.Bold = True
'oComment.Range.Delete 'set the comment to no value
oComment.DeleteRecursively 'optional
Next oComment
lbl_Exit:
Set oComment = Nothing
Exit Sub
End Sub