Or remove them from anywhere, though I’m not sure why you’d remove shortlinks from your own author’s posts.
I’ve written a small plugin that will filter your comments using preprocess_comment which is a useful filter comment data before it’s committed to your database. The other toys I used are wp_extract_urls and wp_remote_head to make http head requests to web sites.
The plugin works like this: you feed a function a URL and it gives you back a URL but with shortlinks you get the real destination. It uses wp_remote_head() to make an http HEAD request and looks for the location header.
If it finds that header then it recursively calls itself to get real destination up to 5 requests. After 5 requests the URL is replaced with the # sign. If it doesn’t find that header then the original URL is returned.
Depending on your site that can be a lot of URLs and to cache those results I create transients for those URLs. The next time in a 12 hour window that URL is tested then WordPress will pull the data from the transient.
I’ve never used transients and I’m not sure this is a good idea or not. But if you need to eliminate shortlinks then this plugin might do it. Also this parses all URLs in the post or the comment and that’s probably not necessary. A simple check can be put in to see if the URL is on a list of shortlink providers and ignore all the rest.
You can download the plugin from this Gist page.
Once you’ve downloaded it save it to your wp-content/plugins directory as short-links-begone.php and activate the plugin in your WordPress dashboard. This plugin will not change any post data or old comments. It will modify new comments when they are submitted.