Had a bloated battery, too. My story ended in a very satisfying way:
Friday May 29th:
Late at night my bloated battery pops off the back cover of my Fairphone. I figure this is a serious issue, find this forum thread, write a mail to Fairphone and get an automatic response.
Monday June 1st:
I receive a personal mail from the Fairphone people along with a form that I have to fill out, sign manually, scan and return.
Friday June 5th:
I send back the form (in the days in between I was distracted by other tasks, just my ‘fault’ not to return the form earlier).
Tuesday June 9th
The new (and free of charge) battery is in my mail.
Once more - pretty satisfying!