I'm facing similar problem too. I run a website about hotels in a certain country. All of the hotels listed have their own html page with detailed description, contact details, location, picture gallery...On each page I have a "contact now" and "read comments" buttons that link to php pages of "low quality" but useful for the users. I can't delete those low quality pages as they are useful part of my site but I can noindex them, but in case they still count for site quality a noindex tag wouldn't do any good, would it?
What would you suggest as a best solution? I'm thinking of changing the main hotel pages to php and putting the contact and comment forms on them and then 301 redirect the contact and comment pages to the main (php) one and the main html to main.php.
The idea was to keep the main part of the site in html but obviously if I add comments and contact forms to the hotels pages I'll have to change to php. Will switching from html to php harm my serps?