@HBruijn: Yes, that's my reasoning. Port forwarding has nearly never a place in a proper production environment and having to use it is a strong indication for either a home or a dev environment, both of which are off-topic.

Just enough to enable you to help yourself. In some cases, a simple product name might be enough, but in others a short explanation how a complex product is supposed to help would be necessary. (Not so good ) examples: Q: Want to sync dir tree. A: Use rsync would be OK, but I want central auth for my Windows clients would require more, e.g Use Windows server. It has a component called Active Directory that is meant to do this.

@AlexKey That question is eight years old. Server Fault was very new back then and the view about what are acceptable questions has changed a lot over the years.

Yup, the review system and especially that very common error situation sucks big time. Sorry, but the Stack Exchange staff appears to disagree and left that system essentially unchanged for years now. I stopped reviewing because of this...

@JohnO: Context matters. Server Fault exclusively cares about production use. If your use case is developing or testing (Docker is often used for this and it's the only viable use for Docker/Mac to begin with), your question is off-topic and Stack Overflow is a better place for it as that site also deals with dev tools in general. If your use case is production use, you should have made that clear.

For what it's worth, I would have closed this as "unclear what you are asking", because your question is just that - very unclear. You don't talk about your environment, your purpose, what exactly you tried and how exactly that failed - "it barfs" is by no means an acceptable error description here. Also, you added a screenshot about Docker for Mac, which is decidedly a development environment not meant for production use (any dev environments/purposes are off-topic on Server Fault).

Please note that downvoting on Meta merely signals disagreement with a post - so nine people don't think that your question should have kept open. That's all there is to it.

Works for me, even with a cold browser cache These images are supplied by an external service (Gravatar, a Wordpress/automattic service), so I guess there is not much SE can do about this and the problem lies between you and Gravatar. The images that are working come from SE's imgur subservice.