Discovered my RSS feed was truncating my posts because my Life On Mars/Ashes to Ashes post was so long..... turns out there's no setting to toggle this in the OctoberCMS RainLab Blog, I had to go edit some code.

In case this ever turns out to be something you want to fix, you should change post.summary to post.content_html in /plugins/rainlab/blog/components/rssfeed/default.htm

post.summary truncates your post, while post.content_html shows the whole thing. if you pass that into |raw, this will not escape the HTML characters, which is nice on a template page where you need it to parse something, but as it turns out will break your RSS feed since it's expecting that stuff to be < and > instead.

Anyway OctoberCMS seems to not be that popular so this stuff isn't really well documented, someone's going to try and do this one day and find this page. Good luck to you. Oh and you'll probably be googling the phrase component blogRssFeed so I'm going to drop that here too.