if you set a content such as this in your template :
<h1 id="title">
<?php sf_simple_cms_slot($page, 'title', 'Title') ?>
</h1>
And your slot, should be as simple as possible : basic text. Then you would obviously pick Simple Text as slot type.
The issue here is that is uses simple_format_text() which always returns your text wrapped in a <p></p> tag.
A clean solution is to implement a new slot type such as sfSimpleCMSSlotBasicText which would return text as such (tag stripped), and would be editable in an input text tag.
See the file attached and add it to modules/sfSimpleCMS/slotType/
And add in apps/<my_app>/config/app.yml
sfSimpleCMS:
...
slot_types: # Available slot types
BasicText: Basic text
...
