In the feed there is both a description tag as well as a content:encoded tag for each item, Newsblur usually uses whatever is in content:encoded as the feed story content (in feed view) but every now and then what’s in description is used instead. I haven’t been able to find a pattern in when which is used (besides not having seen the issues with longer posts).
This is a bit annoying as while the description tag contains the full post it doesn’t contain any of the formatting such as paragraphs or blockquotes (besides the link suggesting you become a member), content:encoded does.
Well, that explains why it only happens for shorter posts. In the summary the sites “please consider becoming a member” line always seem to occur twice, one without any formatting and once with the same formatting as it has in the regular formatted content.
If the post is short enough and the formatted content doesn’t contain enough html tags to make up for the repeated line the summary would then be longer.
Using the summary if it is longer seem like a reasonable enough way to do it since it really never should be, being a summary and all, so I guess I should go bother them about fixing their feed.