I have a blog in a Community server based platform, and I would like to move it over to Wordpress. Since it's a community I'm already part of, I don't want to lose that community regular readers, so I am planning to cross post every new post I make at the community server's platform. I'll post the title of the blog, along with a short description, and a link to the post on wordpress. How is that going to affect SEO? Anything I should be aware of? I care only for the SEO of my new blog at wordpress, the other posts at the community server platform are there just for the record.
After changing CMS systems the biggest problems is the usrl`s , the search engines send the users to old links and they get 404 pages[or to your old blog] and you lose them.
If you can create redirects to the new WP website to lose less traffic and visitors as possible.
About the posts that will stay on the old platform "just for the record" if you use them again in your new site you can get punished for duplicate content.