With this particular kata over multiple days my submissions are failing with errors like:

"Submission timed out. Please try again."

I'm submitting in C# and wondered if anyone else has had similiar problems?

Right I get it now ta, seems I completely misunderstood what you were saying in the kata description.

I think downvotes should be supported. I can understand why you haven't added them but to me the current system doesn't seem to me to be working, I say that because the quality of katas is highly variable and some of them are surprisingly poor. I have logged comments for some of them but really the best solution would be to allow me to downvote and force me to add a comment for the author explaining my issues. That way the author gets feedback and I have done my bit to ensure other people know that there are potentially issues with the kata and that they might want to consider skipping it.

Still don't understand to be honest:

"In a sequence of numbers from 1 to n (n > 0 given) a friend of mine has removed two numbers but it tells me that the product of the two removed numbers is equal to the sum of the numbers he left in the sequence.

Sometimes he cheats and it's not true."

I guess to me it isn't clear if he's lying about removing numbers, or if he has removed two numbers and is lying when he (it?) tells me that the product of the two is equal to the sum of the rest of the values in the sequence.

No odds to me as I lost interest and just looked at solutions so it wouldn't show up for me in future but I thought it might be worth clarifying in case others are confused.

To me the quality of the kata's varies wildly so I'd like the ability to flag individual katas as being ones I don't ever want to see again.

"Sometimes he cheats and it's not true."

Maybe worth specifying what is not true, is it that there is no numbers missing, or that they don't sum to the same sum as the array as a whole?