Learn English – Clauses, and comma before “nor”

You are assuming a rule that I believe is a pseudo-rule (perhaps you could quote this 'rule' from some grammar?) I'd personally have no trouble with

Tom went to France and Dick went to Belgium.

It's clear enough. The addition of a comma before and would not worry me either - I'd add a pause if reading that version.

Here is an endorsement of the optional dropping of that prescriptive comma:

When a coordinating conjunction connects two independent clauses, it is often (but not always) accompanied by a comma:

Ulysses wants to play for UConn, but he has had trouble meeting the academic requirements.

When the two independent clauses connected by a coordinating conjunction are nicely balanced or brief, many writers will omit the comma:

Ulysses has a great jump shot but he isn't quick on his feet.

( http://grammar.ccc.commnet.edu/grammar/conjunctions.htm )

What disturbs me far more is the rambling and over-punctuated nature of the example sentence. Two at least are needed - the garden-path flavour of the original might even lead some to misconstrue it, being led to believe that ' the subject of the two independent clauses is the same'.

I would say that it is wise to remember that the comma is a way of representing a pause, that the speaker makes, whilst talking.

In this case, as Lawrence points out in his comment, the clauses are rather short, and so there is no real need for the speaker to pause, to take a breath, or emphasise the first clause. Therefore, in this case, and other cases with short clauses, the comma can be omitted.

However, it should be noted that, one could still use a comma (in reported speech), if desired, in order to provide emphasis, by pausing, in order to allow the meaning, or significance, of the first clause to sink in to the listener.

That is to say, if the speaker, who is an invitee, was trying to avoid offending the listener, who could be the inviter, by refusing the invitation, pausing after the "I'd like to go" gives the impression that the speaker has a desire to participate (even if they don't really want to), before stating why they can't.