Google seems to have added a message button to the “updates” section of the Google Local panel view. So these are where you can add updates through Google Posts on local, but there is a message button there for a customer to ask you questions about that update.
This was spotted by Darcy Burk and posted on Twitter. Here are some of his screen shots:
The consensus of the local SEO community is that this is a couple weeks new.
Forum discussion at Twitter.