I've reworked the RSS feeds for this blog, and you should now be subscribing to individual user RSS feeds. If you're seeing this post show up as a new post in an RSS feed, you're subscribed to the sitewide feed. You probably don't want that.
You probably want to be subscribed to posts by arjun, if that's what prompted you to subscribe. In contrast, rjn is a newly created account that I intend to use for higher-volume shorter-form blogging. Now if you want to be subscribed to that stuff, you probably want to also subscribe to its own rss feed as well.
At some point I'm going to be adding in some more user accounts that simulate spammers (my intention is to build a platform resilient to spammers), and things like that, so I'll be deprecating the sitewide feed before I do that.