Make generic filtering warning more eyecatching

Author: benjie

src/pages/postgraphile/filtering.md

@@ -25,10 +25,21 @@ adding fields using [custom queries](/postgraphile/custom-queries/),
 [makeExtendSchemaPlugin](/postgraphile/make-extend-schema-plugin/).
 
 You can also augment PostGraphile's existing connections using custom
-[Graphile Engine plugins](/postgraphile/extending-raw/), such as:
+[Graphile Engine plugins](/postgraphile/extending-raw/), such as the following: 
 
 #### Filter Plugin
 
+> 🚨**BEWARE**🚨: adding powerful generic filtering capabilities to your
+> GraphQL API is strongly discouraged, not just by Benjie (the maintainer of
+> PostGraphile) but also
+> [by Lee Byron](https://twitter.com/leeb/status/1004655619431731200) (one of
+> the inventors of GraphQL) and various other experts in the GraphQL ecosystem.
+> It is **strongly advised** that you add only very specific filters using one of
+> the techniques above (and that you make their inputs as simple as possible)
+> rather than using a generic filtering plugin like this. Not heeding this advice
+> may lead to very significant performance issues down the line that are very
+> hard for you to dig your way out of.
+
 A very popular plugin is Matt Bretl's connection-filter plugin, located at
 [https://github.com/graphile-contrib/postgraphile-plugin-connection-filter](https://github.com/graphile-contrib/postgraphile-plugin-connection-filter).
 This adds a `filter` argument to connections that enables you to use advanced