You apparently don't know that "simple mafia" is played everywhere else on the internet and in real life, and no one uses clues of any variety, and the quality of those games and players tend to be much higher than here, even on random obscure sites similar to this one.
I do happen to be aware of this, but I dispute your assertion that their games are automatically "higher quality" because they don't have clues.
I already explained why this is, several times. There is no logic involved in clues.
By this same token, there is no logic involved in normal behavioral analysis. A player never has 100% definitive information regarding another players actions, unless their power gives it to them. Another player can always be lying when you think he's telling the truth, or vice versa. By symmetry to your argument, Azrael: You say "I think X is guilty" and other people say "Yeah I think X is guilty too" and your only recourse is to say "I'm not guilty." The only difference between this and clues, is that in the case of clues the source of ambiguity is the interpretation and the analytic material is the clues, whereas without clues the source of the ambiguity is the other players and their lying skills, and the analytic material is the actions of the [power role] players. Bad clues are similarly analogous to posting screenshots or verifying legitimate copies of a Role PM; these are destructive to the game in exactly the same way a bad clue is, and are not allowed for this reason. Unfortunately the "goodness" of the clues is dependent upon the skill of the host, and cannot simply be "not allowed" like role verification.
No one can add or contribute anything to this [a clue interpretation], since it's an interpretation of something the host did
I can disprove this by direct counterexample: Suppose a clue interpretation as directed at player X. Detective Y, who investigated player X the previous night can add "No that clue can't refer to this person, I followed him the previous night and he neither visited anyone nor was visited by anyone."
Every effect that clues have on gameplay is either negative or neutral.
We have already pointed out some positive effects. I agree that if the clues are obvious or too easy, or contain no ambiguity whatsoever it does detract from the game in a negative way, but the existence of good clues can add a dimension to the number of behaviors we can analyze, as well as giving normal townies another way to participate without having an explicit power role. Clues can be balanced into the game just like any other power role; an extra mafia hitman can be added to account for their presence or something. It's like giving the town a collective power, and just like any other power (BDS hitting a townie for instance) it can be used both to help and harm the town.
You are of course entitled to prefer games without clues; I just hope to help you see why there are those of us who do find clues fair and fun. And of course to voice my support of clues for this game of mafia.
None.