Please check it out
http://validator.w3.org/feed/check.cgi?url=https%3A%2F%2Fmeta.discourse.org%2Flatest.rss
This feed does not validate.
line 27, column 54: link must be a full and valid URL: /t/rss-issue-link-must-be-a-full/28321 (30 occurrences) [help]
<link>/t/rss-issue-link-must-be-a-full/28321</link>
^
line 33, column 10: url must be a full and valid URL: /t/rss-issue-link-must-be-a-full/28321.rss (30 occurrences) [help]
<source url="/t/rss-issue-link-must-be-a-full/28321.rss">RSS issue ...
^