According to some references below, I assume nginx would downgrade strong etags to weak ones when it modifies response content (e.g. gzip compression). But nginx removes strong etags on gzip compression instead of a downgrade.
- http://nginx.org/en/CHANGES (See "Changes with nginx 1.7.3 08 Jul 2014")
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*) Feature: weak entity tags are now preserved on response modifications, and strong ones are changed to weak.
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- https://github.com/nginx/nginx/commit/def16742a1ec22ece8279185eb2b798eb5ffa031
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Entity tags: downgrade strong etags to weak ones as needed.
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