Why do I encounter a strange phenomenon when putting links in an answer?

I just answered a question, and I included sources at the bottom of the answer. I discovered that I could not put ”.com” or ”.org” in the name of the link, or it would not take me to the right place. For example, when I linked 4Paws.org, the link went directly to the main page of 4Paws instead of the page I wanted. However, when I changed the link to 4Paws, it worked perfectly. Why does Fluther override the usual linking system when you add ”.com” or ”.org” to the name of your link?