The attributes are added by the Jetpack plugin, and they’re there because none of the links are actually links search engines can index.
They don’t point to real pages, they’re just placeholders before each Social Network is loaded.
Here is what Google has to say about nofollow links: Use rel=”nofollow” for specific links
Here are some cases in which you might want to consider using nofollow:
– Untrusted content
– Paid links
– Crawl prioritization
“Crawl prioritization” is relevant here: Search Engines can’t share your posts on Social Networks, so there’s no reason to invite Googlebot to follow these links. Using nofollow on these links enables Googlebot to crawl other pages you’d prefer to see in Google’s index (like other posts from your site).
You can consequently leave the nofollow attribute here as it is actually good for those links not to be followed by search engines.
