9/28 Jonh - We don't support users changing EnvoyFilters directly. Any change could be lost when the operator reconciles the SMCP.

Documented here https://access.redhat.com/solutions/5672521

10/13 Rob C We do not officially support EnvoyFilter.  Upstream Istio does not support them either. 

The background here is that EnvoyFilter patches are very sensitive to the format of the Envoy configuration that is generated by Istio.  If the configuration generated by Istio changes, it has the potential to break the application of the EnvoyFilter.

CSA -I think the confusion stems from our documentation (which says nothing at all about whether or not EnvoyFilter is supported, but does specifically tell customers to use it for normalizing urls [1]) and from the knowledge base article's specificity around versions [2].

 
[1] [https://docs.openshift.com/container-platform/4.6/service_mesh/v2x/servicemesh-release-notes.html#configuring-for-case-normalization]]
[2] [https://access.redhat.com/solutions/5672521]
Also, from other e-mail threads

"EnvoyFilter is not supported, as it relies on the internal structure of the Envoy configuration generated by Istio.  If the structure of the configuration changes (e.g. because of a bug fix, new release, etc.), the filter may not apply correctly.  Use of EnvoyFilter is roughly equivalent to programming against an internal API, i.e. there are no guarantees what you're writing against will not change."