Hi,
at Manual:Varnish_caching you inserted a configuration snippet for Varnish to not cache 5xx backend responses. As far as I know Varnish doesn't cache this responses by default. Can you give my a hint why do you think it's important to insert this snippet anyhow? Thanks.
Hi, I added it because my Varnish cashed 5xx backend response, and it was not very nice.
In a default configuration of Varnish 6.x (and also lower versions) it doesn't cache 5xx backend responses - have a look at the Varnish User Guide. I think this snippet doesn't change Varnish's behaviour in a default, untouched setup.
I have no idea what you call untouched setup, but my Varnish version 5.2.1 revision 67e562482 cached 5xx backend responses until I added the rule to not cache it. Also I faced this problem several times on others wiki. Especially when SMW is installed and after you ran maintenance script a lot of pages were cached with the message that MW in maintenance mode. I'm really glad if your Varnish does not cache 5xx backend responses. But my experience says me that this rule should be added.