What I have learned so far:
Several useful features require a thirty six dollar upgrade.
I found something resembling end user documentation. It's a wiki and a set of FAQs. A lot of the information is out of date and none of it appears to have been written by native English speakers.
I can't find the comment moderation page. I've found a page that says "Moderation", but it's blank.
I figured out how to display a Gravitar, but it is not retroactive. The process is to click on the blank picture and get the picture from some other account. Today, at least, the connection time from Echo to those other services is over a minute.
In order to change the appearance of the comment page, I need to hack the code.
Changing the order of the comments from newest on top (their default) to oldest on top (the standard in almost all blogs I read) requires disabling one of the primary features of Echo (live comment updates) and hacking the code.
The only way to the code is to go to my Blogger template. I don't have a Blogger template; I have a homemade one. I have no idea where the Echo plug-in lives.
I may have to go back to my original plan of modifying a Blogger template to look and work the way I want it, and enabling Blogger comments.