Five of your friends took a week-long vacation. You know that in this group not every one is a perfect truth-teller, and if someone is a liar, he is a consistent liar.
Since they know you are an avid puzzle-solver, they decided that each day one of them will send you a message, regarding their attitude towards truth-telling.
The sequence of their messages is as follows :
Monday: There is exactly one liar among us.
Tuesday: I am not a liar.
Wednesday: There are exactly 3 liars among us.
Thursday: There are exactly 5 liars among us.
Friday: There are exactly 4 liars among us.
On Saturday you were asked:
Were you able to reason out how many of us are LIARS?
If yes, on what day; if not, at least what have you figured out?
You say, inter alia, " not very difficult or interesting, so I have no idea what the puzzle author intended."
You repeat it twice !
I must revert:
adjective ˈin-t(ə-)rəs-tiŋ; ˈin-tə-ˌres-, ˈin-ˌtres-; ˈin-tərs-
: attracting your attention and making you want to learn more about something or to be involved in something : not dull or boring
You have used the word not quite in its right context: by getting involved in the process of solving you testify that it attracted your attention.
Not only that - while posting your solution, you never complained about the nature of the riddle, calling it “dull“, ”boring” or “more of the same”.
Full Definition of DIFFICULT
1: hard to do, make, or carry out: arduous <a difficult climb>
2: a: hard to deal with, manage, or overcome <a difficult child>
b: hard to understand : puzzling <difficult reading>
For d2 it should not be very difficult, but it was difficult enough for 2 persons (at least) to base their solutions upon facts not implied by the puzzle and therefore post erroneous answers.
As per your rating - I cannot blame you, - your conclusion was based on false assumptions, and it is always easier to blame someone else, justifying yourself.
I still expect some solver to post the correct answer and to address the standing of the puzzle.
I consider my riddle challenging enough to read, understand and solve (not necessarilly post).
Edited on December 24, 2014, 10:30 am