That is fraud, assuming it was sold under an agreement that it should work and the seller disclosed all knowledge of problems, because the seller would be committing fraud by withholding that information.
How is that comparable to insider trading? There is no fraud involved with insider trading.
If the seller of stock fails to disclose all knowledge about problems with the company would that seller be committing fraud by withholding that information? It seems to me that the comparison is quite easy to make.
Yes, if the stock is sold under the agreement that part of what is being sold is everything you know about the company. Stocks generally aren't sold under such pretense or agreement and never have been (at least not any stocks I've traded).
Someone has to buy the stock from you; if you know that there are issues with the stock and they don't, that sounds like pretty much the same situation.
How is that comparable to insider trading? There is no fraud involved with insider trading.