"You are not allowed to create or update this content" in Apple Communities discussion forums. That was driving me nuts as well. The workround is as follows until Apple fully fixes the issue:
- Make sure you set Safari to Preferences Advanced Zoom 100% (150% causes the issue) to see content that otherwise does not show on large Apple Display 22-inch (!!!).
- Select forum. That is critical. If you cannot, search for it. For instance, search for iMac to show such forum and select it.
- Select section (click the appropriate button; for instance, Display). That is also critical.
- Post, and now it works.
Apple, please, please, please, fix it. This is frustrating and did not happen before. It is the new forum design. Thanks.