Front end Entry form with validation error support? The official example ( https://craftcms.com/docs/templating/entry-form ) seems to assume that the form itself is not already on a page which is an Entry. Dropping this form into a template that has an entry loaded already spits out that entry's entry.title or entry.body.

How should this work? We want the "new entry form" to live on a page that the client controls the content for.
The saveEntry controller used by the default example returns an entry variable with the newly created item and the applicable error messages. This could be a potential cause of conflict if you have another variable called entry, which is by default pre-loaded in entry templates. 

I think you could create a (for example) product.twig template and manually set an entry variable (via ID or slug) called anything else than entry.