I wanted the same thing, and whipped up a few patches to do just that:
https://github.com/vincebusam/selfoss/commit/263cb1e556afce066d07ad68a6fffe8a7ed64b3a
https://github.com/vincebusam/selfoss/commit/da92ee84b1c8c0af1346826e7e2bb404f5e42af2
https://github.com/vincebusam/selfoss/commit/bba67e02eb0681200892b1222729d7e2414b8d49

I also have a new updated script, in python, that does less sanitizing of the incoming html.
https://github.com/vincebusam/selfoss/blob/master/scripts/update.py