Two ways around this:
- if you are editing your Ditto call using the rich-text editor (TinyMCE), yes, tags and so on will be turned into entities like this. You can insert a line break in TinyMCE using Shift+Enter in the editor, and that should be preserved in your output. But it makes your snippet call look rather messy.
- instead of using &dateFormat in the snippet call, you can use the built-in PHx (placeholders extended) output modifiers in your template chunk. There is a modifier for date, so your output chunk could read:
<div class="myDateBlock">
<p>[+createdon:date=`%b`+]</p>
<p>[+createdon:date=`%d`+]</p>
<p>[+createdon:date=`%Y`+]</p>
</div>
Ditto has built-in PHx for handling its output chunks. See the Wiki (
http://wiki.modxcms.com/index.php/PHx) fr details of how it operates.

KP