Maybe do a "Ask HN: How can I improve my team, business model, etc." and we can all crowd-source improve your idea so that another angel group would be interested in investing.
But rejection is rejection. I wouldn't try to sugar it up too much. Reality is a good teacher.
I used to be a freelance writer. You pitch people, they reject you. When asking girls out, you ask them, they reject you. If you're a salesman, you make friends and offer people help, they reject you.
Nothing wrong with being rejected. In fact, it should be a point of pride. Life is a numbers game. You have X rejections to get through to get where you are going. You got rejected. Now you have X-1. The faster you can crank the decrement loop the faster you'll reach your destination (assuming you are learning each time through the loop, of course!)
You're in a conference. The keynote speaker says something cool. You go to tweet it to your friends -- but it's longer than 140 characters. So you key it into your iPad on my app and choose to share it with your FaceBook and MySpace Friends. Over on FB and MySpace, the longer quote appears and has a link back to my web app where the quote is stored.
You're reading a political or science article. About half-way down, the author makes a really cool point -- all the ideas seem to be coming together and this text just jumps off the page. You highlight the paragraph and enter it into my app, choosing also to share it on Twitter and FB.
You're looking for something pithy to tweet or put on your FB status. You visit my app and read the latest quotes from sources all over the world, sorted and ranked especially according to your tastes. Choosing the one you like the most, you upvote it, make a comment, and choose to automatically email it and post to your status updates.
You're looking for the best of the web today. Visiting my app, quotes from much longer articles and speeches are listed, customized to your tastes. Finding one that looks especially interesting, you click the link and go to the longer article, spending 10 or 20 minutes reading the full text.
Your friend hears something incredible at a news event. He quotes the speaker, links to the video, and notifies you by using my app. You visit his quote on my app, make some comments, and vote it up. Soon you and your friend have made several comments -- other people have also joined in. Your conversation about this quote is saved for you to return to when you like.
Finally, you're reading a book on your Kindle or other device. You find a particularly interesting passage. Quickly you copy it out, tag and save it, perhaps also choosing to share it on your status update. Later on, when you are not at your e-book reader, you can visit the web site and view your quotes -- along with the comments from your social network and other folks who share your same interest.
Does that describe it well enough?
2) Better content preference learning system
I still don't know why anyone would use this when you can do all this using existing microblog services like Twitter, Posterous, or Tumblr and it's obviously already exists in social networks like Facebook and Buzz (status updates with comments).
1) Message length
2) Content preference learning system
3) Niche product
I think there could be room for single-use publishing ("I want to store and share something easily, but not make a habit of it like a blog"), but I don't think saving quotes and inspiration in the way you've described will take you places.
After all, the entire point is to have a solution to start with, which might just be a personal itch, then pivot the more you interact with customers.
The pivot is key. You and I or a hundred other folks could debate for hours the merits or drawbacks of a particular solution. The key thing here is that there is a direction that is very clear, yet also very changeable. Customer development is much more important than initial vision, but that doesn't mean you shouldn't have an initial vision.
EDIT: One of the interesting things I found looking for a partner was dealing with folks and initial visions. Either nobody could agree on one, in which case nothing could get started, or potential partners were so attached to a particular vision that it was going to impeded the required later pivot. It's hard to be motivated about something you know is wrong (to some degree)
Next you'll tell me the tag line isn't descriptive enough. Fair enough, but it goes to show that these show-and-tell startup games have a lot of room for subjective opinions.
Describing a startup using usage scenarios is not uncommon. Peter had a problem with the old description. I felt that usage scenarios would explain the most with the least amount of fuzziness, so that's how I edited it.