Google+ Communities now allows you to post directly from your Google Gmail account online.
- Visit https://mail.google.com
- Login with your details
- Open the email notification and towards the bottom you can make a comment or reply (See below example)
NOTE: We personally love this feature as now you can reply quickly to a postings. Plus as an extra awesome bonus if you had the email sent to you an hour ago and a few people had commented since you will get the updates in your email message.