This issue refers to the “1 comments” text within the blog post preview default transformation (e.g. cms.blog.PostPreview). The “s” letter apparently resides here - the linguistic aspect is not preserved.
Therefore, if you want to display this text correctly, you can either create a custom function to transformation or even more easily use the IfCompare built-in function which does it for you:
<%# IfCompare(BlogFunctions.GetBlogCommentsCount(Eval("DocumentID"),Eval("NodeAliasPath")), 1, "comments","comment") %>
Links to other resources: Transformations documentation