Comment by Sniffnoy

The article itself falsifies this explanation; IE wasn't released until August 1995. The HTML draft specs published prior to this already specified that these tags didn't need closing; these simply weren't invalid HTML in the first place.

The oldest public HTML documentation there is, from 1991, demonstrates that <li>, <dt>, and <dd> tags don't need to be closed! And the oldest HTML DTD, from 1992, explicitly specifies that these, as well as <p>, don't need closing. Remember, HTML is derived from SGML, not XML; and SGML, unlike XML, allows for the possibility of tags with optional close. The attempt to make HTML more XML-like didn't come until later.