For me it’s not about whether or not the image was altered, because you have to alter them somewhat just to get them to look right, either automatically within the camera as it’s taking it, with a lens filter, or in post processing. Usually multiple of those.
The question for me is, is it being altered to make the pic look like what the coral looks like in person, or is it being altered to look “better” than it really looks to justify a higher price? The only way to know is to see both the pic and what it looks like in person where the pic is being taken. We don’t get that option for online sales, so you’re left with whether or not you trust the seller. Some are trustworthy and some aren’t. And it can change over time. And people will have different opinions on which is which even for well known vendors. No blanket statement lumping all online sales together is going to work.
