The bug

1.16.4-pre1 added an undocumented dedicated server property text-filtering-config which allows you to specify an online service for filtering text, such as chat and text of written books.

However, there are certain cases which are not covered by it.
(Note: The relevant field in 1.16.4-pre1 code is net.minecraft.server.level.ServerPlayer.textFilter)

Not covered

• /msg (does not require OP privileges) Fixed in 1.19 Pre-release 1
• /teammsg (does not require OP privileges) Fixed in 1.19 Pre-release 1
• renaming items
  Note: Handling for rejected item name might be rather complicated