Clarification on additional parameters for numeric replies with trailing parameters

[jwodder]

The documentation on numeric replies states:

Clients MUST NOT fail because the number of parameters on a given incoming numeric is larger than the number of parameters we list for that numeric here.

and it strongly implies that any numeric reply can have additional parameters added to it. However, many numeric replies have "trailing" parameters that will almost invariably always contain spaces, meaning that no additional parameters can be added after them. I can think of three interpretations for such replies having a larger number of parameters:

1. If a numeric reply is documented with a trailing parameter, servers cannot add additional parameters to it.

2. If a numeric reply is documented with a trailing parameter, any additional parameters added by a server must be inserted before the trailing parameter and after all other documented parameters.

3. If a numeric reply is documented with a trailing parameter, a server can add additional parameters after it if & only if it sets the text of the (now no longer) trailing parameter to something without spaces.

Clarification on which interpretation is correct would be appreciated.