User blog comment:Rappy 4187/Technical Update: November 18, 2015/@comment-25239866-20151120190512/@comment-5558012-20151120200003

"This may potentially affect some custom CSS - the other H1s (such as the wordmark) have been converted to H2s."
 * Not a bug, look at your CSS regarding h2 (if you mean w:c:el.kanal, you have 20px applying to the top margin of your h2).