Q: How can I create comment forms so people can send me email via the web?
Please Don't
Feedback/comment forms used to be standard on many websites, but recent experience is that the output will receive a lot of spam, and is largely useless. Our recommendation is to provide an email address, and written directions to send you email - that won't eliminate the spam, but the email filtering for spam is fairly mature and will do a better job with it. If you would like to advertise a moira or mailman list, that gives you after the fact control over what address will be known.
Existing Options
web.mit.edu has a cgiemail form, which should be considered strictly legacy.
CMS-based websites often allow webform submissions; our recommendation is that any website feedback through a form needs to be restricted to MIT community members.
Gathering Structured Data
Qualtrics and Google forms are good options for taking in data.