@marciojmendes ~ Please don’t let this issue bother you so much. There is very little that will probably ever be done about it. Please try to focus on why you are using Memrise in the first place - to learn ! People who circumvent the system aren’t learning. They are farming points, but learning or retaining nothing. That’s a useless exercise.
Take a look at the leaderboard picture you sent. @Roberto72 is (really) number one, and you are (really) number 2. You have shown dedication to learning. @Roberto72 is something of a legend in Memrise. He has been a leader for a long, long time, and you are right on his heels. You have shown that you have the capability to learn and retain what you learn. GOOD FOR YOU ! I hope you keep it up.
Please don’t focus on the point farmers. They aren’t worth the time and energy. Please try to focus your time and energy on learning, or being a mentor to people who don’t have the knowledge, skills and abilities with languages like you do. Try to do something positive with Memrise, like the vast majority of us are trying to do. Don’t let what others do tarnish your opinions of what Memrise has to offer, and what you can do with that offer. Learning can be a never-ending experience if you focus your attention and goals accordingly.
Of course you can leave Memrise at any time for another system, but if you do, and if you encounter similar point farmers, or people who want to circumvent that new system, then what do you do ? Do you leave that new system and go somewhere else ? That could be an endless exercise in futility and it’s just not worth it.
If you are learning on Memrise, then by all means continue to do so. Make each day better than the day before. Set goals to learn or share your learning with others. Don’t look at leaderboards, unless it is to guage YOUR progress. What others do is not important, especially if what they are doing runs counter to popular conventions, or in some way brings you irritation. Why put yourself through it. If Memrise staff won’t address the issue, why worry about it. Focus your energy on learning.
As for being a “theif”, I learned (from watching a lot of old black and white Hollywood-type movies) that the only really good thieves are the ones who can do something underhanded and no one notices that they did it. The ones you (and others) have pointed out are not exactly very good at what they do because people are aware of what they are doing. So try not to give them the attention they seem to crave. Maybe if people ignore them, they will go away. Maybe part of the thrill of point farming is seeing how it tends to upset people. If people ignore them, they lose that part of their thrill.
I hope you will continue to learn and grow. You have shown that in the past. I hope it continues into the future. Don’t worry so much about others. Focus on yourself. Accentuate the positive, ignore the negative.