If you get repeat spam comments on your New Wix Blog, you can Block the commentator from posting any more comments in the Wix Dashboard under Site Members. Just click on the three dots icon next to the repeat offenders name and choose "Block Member". This will prevent them from commenting again (at least, under the same email, they can always setup a new login and comment again.
If you are finding that your blog posts are getting tons of spam comments, you can also turn off commenting. Here's how:
Turn on/off Commenting on Individual Wix Blog Posts:
Click the blog in the Wix Editor.
Click Manage Posts (found under New Blog icon)
Click the Show More icon on a post.
Click Turn off Commenting to close commenting on a post.
Click Turn on Commenting to allow commenting.
Turn Commenting On or Off for All Blog Posts:
Click the Wix Blog button on the left side of the Editor.
Click Blog Pages.Select All Posts.
Click the Post Page in the Editor.
Click Settings.Click the Display tab
Scroll down and click Recent Posts & Comments.
Click the Show Comments toggle:
Enabled: Site visitors can leave comments.
Disabled: Comments are not displayed.
Note: Only the Admins can turn on and off comments and only Wix Site Owners can Block Site Members.
found it on the Wix Dashboard backend under "Site Members". :)