@paulgit There's an unescaped ampersand in the blog subtitle. Should be & in the XML. Needs to be fixed by @matigo in the feed generator code ultimately, but I can rename it to unbreak the XML as a workaround for now.
Checked in Pythonista:
import requests
r = requests.get('http://macchiato.10centuries.org/rss.xml')
r.content.splitlines()[27]
# b' <itunes:subtitle>Being the Website & Home of Macchiato, a Stirring Tale of an Underdog</itunes:subtitle>'