It's a similar to the issue with the note plugin (see very first comment in the
plugin's comments section):
It's this CSS bit from the nspages plugin:
.catpageheadline {
clear: left;
}
And after fixing that you'll see that
.catpageeofidx behaves the same way.
You can either delete that line or rather override it in your
conf/userstyle.css (just create it, if it doesn't exist) like so:
.catpageheadline,
.catpageeofidx {
clear: none;
}
By the way, the ACH template is quite old and not completely compatible to the latest DokuWiki version. I planned to update it for a very long time and when I will eventually do it, it won't have problems with any
clear:left etc anymore ...