Why do feral cats not meow? Can a feral cat meow?

I will answer the second question first. Feral cats have the physical ability and anatomy to meow just like domestic and stray cats. The point is that they don't normally meow because the meow vocalisation is a learned one between domestic cat and human caregiver. It is normally a demand for food or attention.

The answer is not quite as clean as that because the meow sound is very variable. People should not think that every meow made by every cat is exactly the same. There is a great spectrum of meow sounds. 

The word 'meow' is an onomatopoeia meaning that it reflects the sound. But as the meow sound varies a lot it does not reflect the meow sound sometimes!

The meow sound has been learned by the domestic cat to make a demand on their human caregiver. Image: MikeB

As to the first part of the title, as mentioned, this is a learned vocalisation by domestic cats over about 10,000 years of domestication. It is a sound developed between cat and human. 

As feral cats nearly always or almost exclusively 'talk' to other feral cats there is no need for them to meow.

The feral cat might hiss and growl at a human but they won't normally meow at them. 

But if you have the patience to socialise a feral cat which might take many months even as long as 18 months if they are an adult feral cat who's lived their entire life in the urban jungle, they will eventually learn to meow at their human caregiver.

It is a learned process and a demand normally. However, it's meaning will vary as the sound's tone and tenor varies.

It may merge into other sounds like a growl. The Siamese cat has a honk to make demands rather than the classic meow. As I said the meow sound varies 😎.

Here's a video of a very strange meow sound but it is certainly a demand. A call for attention.

American Curl turns up in a homeowner's backyard as a stray

This is unusual. Perhaps very unusual. A user on the Reddit.com website has posted a video which you can see below of a domestic cat that they thought had a strange appearance. 

They said that the cat was very big with strange ears. I immediately, identified the cat as an American Curl which is a fairly rare purebred cat and certainly very rare if he or she behaves as a stray cat which appears to be the case in this instance. 

They're not normally large cat but standard-sized domestic cats with one exception to their regular appearance namely the ears that curl back due to a genetic mutation.

Here is an example of an American Curl show cat photographed by Helmi Flick years ago.

Photo: copyright Helmi Flick.

Note: the video below may eventually stop working. Sorry but I can't control its existence. CLICK ON THE EXPAND ICON BOTTOM-RIGHT TO SEE THE VIDEO FULL SCREEN.

What kind of cat is this? Stray cat moved into my back yard. Has huge paws/weird ears.
by u/ReindeerNo1893 in cats

This breed is meant to be very standard in appearance and they can be tabby cats or any other coat type. I suspect that a neighbour of this person owns this cat. 

And the cat has wandered into a neighbour's property as domestic cats do. It is also slightly unusual for a person to allow their fairly rare purebred cat to wander around outside without supervision.

American Curl turns up in a homeowner's backyard as a stray. Screenshot.

An alternative assessment would be that this is a non-purebred cat which happens by chance to carry the genetic mutation which cause the ears to curl back. 

This gives them the appearance of a purebred American Curl. You won't be able to tell the difference because, as mentioned, the American Curl is a very regular looking cat. There are no other outstanding features other than the ears.