Some sellers do not respond to questions, or disable the feature entirely.
Asking a drop-shipper about a listing is unlikely to be fruitful. The drop-shipper may not know enough about the product to answer. Or may not speak English. Or may rightly calculate that any honest answer is unlikely to result in a satisfied sale. Not answering saves the drop-shipper effort and time, and avoids a potentially difficult transaction with a picky customer.
Asking a mega bookseller about whether a particular $5 book includes an appendix is unlikely be productive. Almost any time at all spent answering such a question would cost more than the transaction is likely to profit the seller. The same question to a small-time seller with a dozen listings is much more likely to be answered. More so if it is a $50 book, or a $500 book.
In general, if no response is forthcoming, you should assume that the answer is not a favorable one where the value of the item is concerned.
If you ask a seller whether the $5 book they are selling is the standard edition or the ultra rare gold-leaf edition, there are three potential scenarios: 1) The seller politely answers that it is, in fact, the standard edition; 2) the seller does not respond at all; 3) the seller ends the listing and relists at a much higher price.
Executive summary:
Most prospective buyers ask a question because they are seeking information that will help them put the correct value on an item.
A seller that does not answer a simple, polite request -- or one who blocks all questions entirely -- particularly when the question is regarding a very expensive item, is providing valuable information, whether it is recognized as such or not.
