The reason being Wikipedia is a summary made by a constantly changing group of people out of actual sources with a real name attached to it, which are the ones you're supposed to link.
In any case, a permalink to a specific revision that includes a sha256sum of the article is a good way to ensure you're getting a reliable link to information which can not be tampered without failing the checksum.
If they control the checksum check they can alter it too. Maybe, if you are careful enough to store all the checksums of everything you do online you will be able to tell, but others that see your posts won't even notice.
Merkle trees can help here. Basically a tree of hashes. If you keep track of the root hash, it's easy to prove any individual leaf has not been altered.
In any case, a permalink to a specific revision that includes a sha256sum of the article is a good way to ensure you're getting a reliable link to information which can not be tampered without failing the checksum.