Recently I have been trying to install OpenWrt on my stock TD-W9980 without opening the case. The article mentions the web interface hack and the StatPOSTer tool. I found StatPOSTer to be severely lacking and incapable. After a quick search I discovered the tpconf_bin_xml tool mentioned on the page for Archer D7. It didn't support the W9980 configuration format, so I went ahead and added support for it. The router happily accepts the configuration. However, it should also be noted that the hack does not work on the latest stock firmware for this model. It appears the bug was fixed at some point, and the firmware simply discards any attempted changes to the "Description" field. The article should be updated accordingly.
In the meanwhile, I would love to hear if someone has managed to make a slight variation of this hack -- perhaps some slight change to the modified configuration -- to work with the latest firmware.