After playing Feint do I just discard the shadow card and continue on to my attack on the enemy?

The shadow card stays until all attacks have been finished, even if it no longer has an effect.

It does however still go off. So if the effect says to make you destroy an attachment it would still do so simply because Even though he isn't hitting you in the face the shadow effect is still active. It's rough but at least even though he is not going to attack you you can still choose a defender before playing faint. So you will be able to use your Gondorian Spearman to deal a damage and not take any, or play swift strike. If either of those go off and kill him before the shadow stage then the shadow effects won't flip at all and go right into the discard.

Iron-on Ghost said:

Shadow effects only go off in step 3 of Resolving Enemy Attacks. Since the Enemy never attacks that step never happens. The Shadow card would just be discarded at the end combat phase. At least that is how I read it.

From Rulebook on Page 18:

At the beginning of the combat phase, the players deal 1 Shadow card to each engaged enemy.

This occurs before you choose an enemies attack to resolve. The only time the shadow card gets flipped face up is during step 3 of Resolving Enemy Attacks, so if the enemy cannot attack (Forest Snare or Feint) it will never get turned face up and resolve.

From the Rulebook on page 20:

Shadow cards remain on the enemy to which they were dealt throughout the combat phase. If that enemy leaves play, discard its shadow card from play. At the end of the combat phase, discard all shadow cards that were dealt this round.

Nothing specific here about face-up or face-down. If there is a shadow card on the table at the end of the combat phase it gets discarded.

Brad Harrington said:

You make a good point. So once again we can only guess the designers intent as the term "attack" is loosely defined.

As it sits it would translate that an attack is all the steps combined. so if a creature "cannot attack" the steps are skipped. However the biggest issue with this card is the timing, because in order for you to play an action you have to first choose an attack which is the 1st step in the "attack" sequence. And only after this step are you able to play actions.

So really we just need to know the designers intent as the definition of "attack" is fairly obscure. And until we get a shout out from the man, we will have to speculate. and my opinion is that you're right.