The error message says what the problem is: each phrase inside the if-otherwise blocks in the rule definition needs to occur on its own line. Phrases like ‘link to nathan-chat-alica-1a’, which follow directly on from the previous phrase, aren’t allowed.
That refers to this line:
link to nathan-chat-alicia-3; link to nathan-chat-alicia-1a;
The statements/phrases are marked off by semicola and are independent from each other, and they can (and in this case must) be written on separate lines.
(The examples from the extension have them on one line in some places where it is allowed, presumably to save vertical space, but I’d generally advise against that, and instead recommend putting them on separate lines even in cases where it’s not mandatory, because it’s easier to see at a glance what’s going on.)
So, this should work:
Rule for finding responses to nathan-chat-alicia-2:
if greeted-peter is false:
link to nathan-chat-alicia-3;
link to nathan-chat-alicia-1a;
now greeted-peter is true;
otherwise:
link to nathan-chat-alicia-3;
link to nathan-chat-alicia-2a.