Recently I noticed that some players challenge or accept invitation, showing a RATING, for example over 1600 or 1700, and when the game begins I suddenly see that my opponent's RATING is less than 1300 or even 1200!! this is a very disturbing "bad news!" I'm sure every honest player hate this kind of dishonesty. Can anybody do something about it?
Are you reading the wrong rating? People have different ratings. Bullet, Blitz, Rapid, and Correspondence (or Daily).
Different people have different ratings based on time control.
Some people, like myself, are far stronger at deep thought and taking our time to find moves. My highest ratings tend to be Correspondence and over the board Classic Time Controls. You get to Quick or Rapid, and it goes down. You get to blitz, it is even worse. Bullet? Even worse than that!
Others, especially those who are not very good chess players that thrive on having fast fingers and are good at driving their opponents' clock to 0, even in lost positions, thrive on bullet, and cannot play over the board classic chess to save themselves. They also tend to suck at Correspondence because they move too fast on impulse (which is what you need to do to master bullet) and have no strategic plan.
So you might see one player with a correspondence rating of 2100, over the board rating over 2000, blitz in the 1800s, etc. This would be someone like myself.
Then you have those with a 2400 bullet rating, but an over the board rating of 1100. That is because these people just know how to move quick, and know barely enough to survive for 60 seconds, like putting the opponent in check, even it is loses material, to gain 3 seconds on the clock, but you ask them for a coherent plan, they could not give you a legit answer.
Then, of course, you have masters that are good at all formats and noobs that stink in all formats, but you were asking about why ratings are different. It could be game format.
If all you do is look at the rating their profile advertises, and do not look at the logo to indicate format, you may be mislead. Like if you look at my 2150ish rating, it will likely have something like a calendar icon or whatever they use to indicate correspondence rating, but if you faced me in a blitz game, I am nowhere near 2150. More like 1850.
So that could be what you are doing. Profiles are not lying. You need to look deeper at the specific format you are playing. If you are playing bullet, look for their bullet rating. If all you do is hover their user name, it will usually show whichever of their ratings is the highest. That may not be bullet for everyone. My highest surely isn't bullet!
Recently I noticed that some players challenge or accept invitation, showing a RATING, for example over 1600 or 1700, and when the game begins I suddenly see that my opponent's RATING is less than 1300 or even 1200!! this is a very disturbing "bad news!" I'm sure every honest player hate this kind of dishonesty. Can anybody do something about it?