Here are some things that I have developed my time in reading fanfictions:

Italicized means that they do NOT always apply to my opinions on non-serious stories, i.e. modern AU and PWP; however, they are usually stupid. BOLDED means that I have absolutely no sympathies. I may be a bisexual male, but even I have limits on tolerating absurd nonsense. This is fanfiction, where things can be different from the original, but if there is so much or a major change, then it loses the intrigue of what makes the original story good. I hate writers changing things so much that the story is not longer recognizable, only to use the names just to make it sound great but association.

I consider people who like stories with (1) slash, (2) gender bender, (3) mpreg, (4) incest, (5) bestiality, and (6) harems as twisted. I especially think fujoshi, incest, and harem lovers are just plain scum.

You writers should be courteous and explicitly put warnings in the summary; otherwise, you are just that desperate into tricking people to read your story and earn reading points. You cannot say "Well, I put it in the beginning/end of the chapter" because that is still deceiving people to click your story.

Reasons:

1. Why do you even want to read about straight people turned suddenly homosexual (I am talking to you, crazy dumb fujoshi)? This includes femslash, which is just more bewildering. I am bisexual, but this is annoying.
2. You do know that character will always be that sex, and your character very likely does not even resemble the actual character: by appearance, personality, and even name. Why the hell do you not just label it as an OC? You are piggybacking on the name to hide your ineptitude of developing a character. What is worse is where a character is "reborn" into a different gender/sex; why bother going through a "rebirth" if the character is nothing like the original? I am not transphobic and am friends with trans people, and I accept them because it is their choice, but when you change characters because YOU want them, then it is stupid.
3. This is without a doubt one of the most disturbing concept ever thought of (along with futanari/shemale, which confuses me how guys who consider themselves straight like dicks), and you have to have to be extremely depraved to even enjoy the concept. Thank goodness it does not exist in reality--a trans man getting pregnant does not count.
4. I guess your a fan of the banjos...and diseases.
5. No further explanations needed. Though, you should get rabies shots to keep others safe. You are kidding yourself if you do not think human and Pokemon sex is not disgusting and depraved.
6. No sensible girl would be in a harem. Your girls have got to be extremely dumb, slutty, or have low self-esteem. Why the hell would smart and strong women agree to debase themselves? It is a blatant contradiction to even try with heroines. Reverse harems are not the same; it is simply a competition, yet it is more entertaining and believable to read.