However, the Sight theme has an active excerpt box and that means you can use it to override the display on the front page and display full posts.

On any theme with an active excerpt box you can use this workaround to have full posts on the front page.

You compose your whole post first and before you publish it you switch to the HTML (Text) editor, copy all the code, paste it into the Excerpt box below the posts editor, and publish the post. http://en.support.wordpress.com/splitting-content/excerpts/#creating-excerpts

If you do not see an excerpt box then go to screen options on the top right hand corner of your Admin page and include:
Post – Likes and Shares, Format*, Categories, Tags, Excerpt, Send Trackbacks, Discussion, Comments**, Slug, Author, Revisions, Writing Helper

P.S. On themes that do have an active excerpt function, the workaround works very well but you have to do it on every post you create.

Featured Slider
Sight displays up to 30 of your latest sticky posts http://en.support.wordpress.com/posts/post-visibility/#sticky-posts that have featured images http://en.support.wordpress.com/featured-images/ in a prominent slider on the front page. To add a post to the slider, mark it as sticky and give it a featured image.

Sight featured images
Large: 640 x 290 in the Sticky posts slider
Small: 290 x 290 thumbnails are used on the home, category, tag, archives, and search pages. http://theme.wordpress.com/themes/sight/

http://theme.wordpress.com/