Do I have to use 'location' and 'startDate' for UserComments?

Question

I am using the schema.org type Article in a website. The page allows users to comment on the articles. In Article is mentioned that comments can be marked with the UserComments type. I did that and it worked great for a long time.

Some days ago Google (Webmaster Tools) started to complain about errors in my markup. They want me to add the properties location and startDate to each comment.

Currently I only use the the properties creator, commentTime and commentText.

Why is there a need of adding the above mentioned properties? I don't have a idea what the location and startDate could be for a simple users comment.

(Is this maybe just a Google trick to collect more data?)

Answer 1

Now the failure messages in Googles Webmaster Tools are gone. Looks like Google has solved the problem.

Answer 2

Google is complaining where? The following example is valid according to Microdata and schema.org (and the Google Structured Data Testing Tool doesn’t show any warnings/errors):

<article itemscope itemtype="http://schema.org/Article">
  <h1 itemprop="name">Article name</h1>
  <article itemprop="comment" itemscope itemtype="http://schema.org/UserComments">
    <p itemprop="commentText">Comment text</p>
  </article>
</article>

(I also tested a snippet containing creator and commentTime: no warnings either.)