The second option is the better option.

Quarantine not below the stock location of the warehouse:

Receipt shows 10 to receive, 2 are sent to a quarantine location - total on hand will be 10, but when you drill down you will immedately see 8 are on hand in the stock location and 2 are on hand in the quarantine locaiton.

Perhaps what is confusing is that the forecast will show 10 in both cases. 

What the post was discussing was a push rule for products sent to the quality location (possible with 1, 2 or 3 steps) that automatically creates a Transfer to send those quantities back to the stock location, hence reserving them and making them unavailable.

If you don't want to create a push rule you can do this manually, just create a return transfer for each quantity sent to quarantine. The transfer will reserve the quantity and make it unavailable for other reservations.

Now, when you drill down you will see that while there are no changes to the on hand quantities (still 8 and 2) that for the products in the quarantine location, 2 are also reserved.

If you were to create a Sales Order for this product, you would see that although Forecasted Stock is 10, Available Stock is only 8.

The difference between what is reserved for Transfer operations and what is not reserved is what makes products unavailable.