We're building a blog on a subdomain of the main site. The main site is on Shopify and the blog will be on wordpress. I'd like to keep the user experience as simple as possible so I'd like to make the blog look exactly like the main Shopify site. This means having a menu in the blog that duplicates the Shopify menu. So is it bad for SEO to have someone click on the 'about us' button in the blog subdomain (blog.mainsite.com) which takes you to the 'about us page' on the main shopify website (mainsite.com)?