A rumour is typically enough to warrant an overnight price hike in consumer prices. While for experiencing reductions, consumers have to wait for a few months for the market to "adapt". And in the end, it usually is the consumers that adapt to the increased prices, so companies don't see any good reason to reduce them.

Look at any stock in any stock market that had a highly positive or negative rumour associated. You will see an immediate spike or dip in value and, a slow regression to the mean.

I don't understand why people waste electrons making comments that cannot even be right or wrong without specific data and defined terms.

Which is the case for electricity and natural gas.

Consumer goods that are usually priced at market rate, such as clothing, regularly see deep discounts.

Whom decides what is too much?

That's the theory. Reality: if a company makes too much profit, it's probably a monopoly or have formed a cartel with their "competitors".

However, the recent crisis sent a large number of consumer energy suppliers into bankruptcy, suggesting that actually they'd been keeping too little back rather than fleecing the consumers.

But have you looked at a chart that proves this claim that everybody makes and assumes is true?