@Parallel Black
The artist literally said it was a paid commission. It wasn’t in his/her budget to add details and such, wasn’t part of what she was paid to do. The advice is good, but incredibly unnecessary and you’re making yourself look like a fool by trying to pick a fight. By continuing to argue you’re missing the point of her original reply. Please, take her advice and “begone”.

No

I wasn’t demanding that you to do it a specific way. My advice was extremely basic and it certainly wasn’t presented in a rude way, at least in my initial comment.

Consider this:
“Just something to show this is a stomach and that Izzy has some internal structure”
That’s the main take-away. That’s the most important line in my original comment.
Whereas these-
“a solid wall to show the limits of the stomach and throat, or simply some texture to the back wall and a bit of liquid pooling around the base”
-are just specific examples on what you could do to fulfill the internal structure suggestion. I don’t see how that could come across as rude, and I really don’t see how those suggestions are unwarranted given there’s literally nothing inside of Izzy’s body that would suggest any sense of structure; Sunny’s head and mane are descending into Izzy’s backside and Zipp looks like she’s floating in a void.

It doesn’t matter to me if an artist doesn’t want bare-bones advice about obvious flaws in their paid work, it’s entirely your choice if you take on any of my suggestions and it’s your choice if you want to ignore them.

However, it would have still been nice to be thanked for the offer to help regardless of whether you needed or wanted it.

@Parallel Black
I don’t care about your downvote. You’re clearly being impolite, don’t know what a “flat” picture means, in different art styles and techniques. Not everyone has to draw the way you see it.
Now begone.

@axidemythe
If you want to turn your nose up at free advice on how to improve the look of a paid commission, then feel free to keep the downvote I gave you. Not wanting advice will not stop anyone from giving it, so best learn to take it in stride if you want future commissioners to view your work as better than this flat, structureless attempt.

EDIT: After some extra thought, it makes even less sense not to draw extra detail on a picture someone has paid you for.

@Parallel Black
This was a flat sketch commission, that means I won’t draw anything detailed.
I didn’t ask for anyone’s advice regarding my work, so please don’t to that.

You should try adding some internal details, like either a solid wall to show the limits of the stomach and throat, or simply some texture to the back wall and a bit of liquid pooling around the base. Just something to show this is a stomach and that Izzy has some internal structure, not that vorish flesh suits where there’s nothing beneath the skin can’t be hot as well.

The external version looks totally fine by comparison. You just need a bit of detail to make this one work as well as the other.