Please see Markup in the Monastery, Writeup Formatting Tips and How do I post a question effectively? Also maybe take a look at Perl Monks Approved HTML tags and What shortcuts can I use for linking to other information? Definitely see How do I compose an effective node title?

As you say your data is plain text, it may be enough to enclose each example in  <p> (paragraph) tags. If the text has some sort of internal structure, use  <code> ... </code> or  <c> ... </c> tags to preserve that structure. (Blocks of text enclosed in code tags will be easily downloadable by the monks and this encourages the monks to work on your problem!)

Please, please don't post 50K of text! Hopefully, each text example will be just a few score or few hundred words; I would say 1000 words max per example. Please try to post examples showing the full range of complexity of your data. Please use  <readmore> tags to reduce data "clutter."