Use a pod template file in a Deployment I've been looking at Deployments descriptions in Kubernetes. In the tutorials I've found, the definition of the replicated pods are always a copy-paste of a pod template file.

Is it possible to rather use a reference to the yaml file (or an url) defining a pod (I didn't found any resource telling so)?

If yes, should it be avoided (in order to keep label/selector in the same file for example)?

If no, is there a reason (because Kubernetes wouldn't know if you modified the pod template file for example)?
Yes you can create resources (including pods) from a url yaml using kubectl.  However, just because you pointed to a remote url does not mean that the resource will automatically update.  You will need to either re-deploy when the remote yaml is updated, develop/integrate with a service that handles this, or look into using a tool such as helm to help manage changes.

It does not need to be avoided, you just need to know that it will not automatically update if the source changes.