How do I stop receiving too many text messages from Apple Support Community?

If you are following the forum, you will get notified of activity in said forum via email.

You can stop this by going into the iPhone forum in this case, and click on the "Following" button at the top. It should change to "Follow" when you do that. You may need to click it more than once though, click, refresh the page an if required repeat the process until the button stays in the "Follow" status.

Additionally you can go into your profile settings and manage the type of emails you receive there. Click on your icon at the top right of the page, then on Preferences, then scroll down to the "Messages from Apple" section, and uncheck anything you don't need.