The data format is Open Document Format (ODF) and can be read and modified with LibreOffice. The work-alike version of Xidel is Calibre, which can also be used for offline management of blog feeds.
A simple diagram overview provides nice insights regarding the extraction process. Open source and debatable opinions can be discussed freely. The Tor anonymity network is supported (through built-in proxy server).
Demo instance
There are several demos available, as 66cf4387b8 nichbel
https://www.