Examples of codepoints, etc, are such as email addresses, domain names, IP addresses or ports. Codepoint values may already have been assigned or may become assigned in the future to entities on the Internet.
The IETF has already reserved addresses, names and codepoints in a number of spaces and domains: BCP 32 (RFC 2606 - Reserved Top Level DNS Names) reserved some domain names for use in examples. RFC 5737 (IPv4 Address Blocks Reserved for Documentation) and RFC 5156 - Special-Use IPv6 Addresses) assigned some IP address ranges specially for examples and documentation. RFC4735 (Example Media Types for Use in Documentation) registered one example media type and one subtype under each of the registered media types for example use. Other similar specifications and reserved codepoints exist.
The IETF should minimize any potential impact on the entity having been assigned such a codepoint from unwanted traffic or other concerns. To help ensure this the IESG will expect the author of any Internet Draft that defines a new specification to use values assigned for examples whenever possible. The IESG also recommends new protocol specifications creating new codepoint, address or names spaces to consider if some part of the space should be reserved for documentation and example usage.