I'd had the same original problem pfefferle notes above.

Note also that some of the fields in the User Profile that are used to add rel-me tags are also used by other plugins occasionally and they're not all done in a standard/canonical way. (Does WP specify if they should be full URLs or just usernames anywhere?) In particular, the popular "All In One SEO" plugin (1 million+ installs, which competes directly with Yoast) and is fairly ubiquitous uses some of these social media fields (typically with full URLs so https://www.twitter.com/username instead of @username or even username) to add meta-data in their plugin.

It may be better to include all these accounts separately as their own data fields within a freestanding plugin so there isn't any conflict with other plugins that may not use them canonically.