After investigations, commit the proposed patch by kklimonda presented with the following introduction : cm/templates/site/login_form.html template uses a relative url for the form action, which seems to break deployment in the subfolder when trailing slash is missing (the form redirects to the upper folder breaking login). Using {% url login %} (as in the attached patch) instead would fix the issue.

from setuptools import setup, find_packages

setup(
    name = "comt",
    version = "2.0-alpha1",
    url = 'http://www.co-ment.org',
    license = 'AGPL3',
    description = "Web-based Text Annotation Application.",
    author = 'Sopinspace',
    author_email = 'dev@sopinspace.com',
    packages = find_packages('src'),
    package_dir = {'': 'src'},
    install_requires = ['setuptools'],
)