here at Renderosity, there is no access to a merchant's email address.  it used to be that one could find it in the ReadMe prior to purchase, but that can now only be found in the ReadMe that accompanies a zip file, thus only accessible after purchase.

a person can use the "Contact" link here to ask a question via the IM'ing system.  it is the only way that i'm aware of to contact a merchant [unless i want to see if they have a current website up, visit the site and see if i can find an email addy that way]. and as a merchant here myself, it keeps all inquires to me in one location, so i don't need to go "trolling for questions" - they're all right there in my site mail inbox ;)

**The stores all have a email address for them to contact me , and I check emails daily, so a customer problem reported to a store I will see within a day , and normally reply same day.
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here at Rendo, the Staff encourages a customer to contact a merchant directly with questions or problems after purchase, etc. before becoming involved, so you're lucky that wherever it is you sell, that the staff there will immediately forward inquires to you & act as the middleman, so to speak. :))

as i said, i try to do my homework beforehand as i don't feel that i should just go about asking questions that i can easily resolve on my own.  and i think it's great that you provide what you feel is all the info required for someone to make an informed purchasing decision.  however, not everyone manages to do that, and i've seen requests from time to time in the Vendor forum here where a person wants to know how to edit/update their ad copy for any number of reasons.  people make mistakes, forget to include info, etc.

you want an example of a question - i'll give you an easy one, though most folks include it in their ad copy as standard these days, but now & again, someone doesn't...

example:
what size are the textures that are included in your merchant resource pack?

a different kind of example?
i have a promo ad where the figure is wearing an item of clothing that is sold over at Renderotica.  i purposefully did not disclose anywhere in my ad copy or images where the item came from because it wasn't too long before that that Renderosity made the decision to not sell erotic items, and i was concerned about listing a site that may be deemed inappropriate.  so i didn't include credit for the item.  but i can tell you that i've had a handful of folks contact me via IM wanting to know what it was & where to find it.  each time i've fetched the link, explained that there are several versions of the item, etc. and answered the question.  takes me literally all of 2 minutes, tops, too.  and i've received back in response from most folks who have asked notes that say thank you, how much they appreciate my quick response, that that isn't usually the norm of their experience here when asking questions of merchants.  and frankly, that's kind of sad, imo.

another way to look at it is to think of having that kind of experience offline, and just how acceptable that might be to you if you were the customer [and i'm using "you" in general terms, and not "you" as in any personal sense]...
  
you go into a store, wander around, read the back of the box for an item, pull out the item's manual from inside & read it, but find you still have a question.  so you seek out the only sales person available, and who also happens to be the store owner, and ask them your question.  you know they heard you [parallel: you know your IM was read], but the sales person wanders off to go do something else without a word, or even acknowledging that they'll come right back.  how long would you wait before feeling like the store owner must not really give a damn about your potential business?  how long would be acceptable?

**I normally put up one picture of the item with material zones simply colored , no texture or bump maps  because it shows how hard or easy changing textures will be .
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btw, i LOVE promo pics that do that.  that gives tons of good info that way on a model's potential. :))