I started thinking I had an Anal Fissure, then went to my doctor originally because I also had hemorrhoids. Those are all gone, and I did end up having a Fissure which the doctor's advice made worse or gave a partner. Hydrocortisone was given for both. I literally almost fainted and had ringing in my ears for a half an hour after trying my second suppository, maybe because my rectum is tiny.
I consistently read around here that Hydrocortisone doesn't help with fissures, and may even make them worse by thinning the skin and preventing healing. Why, then, do so many recommend it? Or does it help with some, but not with others?

Hydrocortisone helps with the inflammation, and if a wound is stuck in the inflammatory phase, it can help calm some of that down, and along with the calming of the inflammation, there will be an easing of the pain. With the easing of the pain, the sphincter will relax more. Prior to the time when there was the option of using nitroglycerin, nifedipine, or diltiazem, hydrocortisone was really the only thing a doctor had to offer for the pain to try and get a fissure to heal without surgery. Sometimes it does help, particularly if there is a fissure plus hemorrhoid (which is common). But it should only be used for a short time, two to three weeks, as yes, a consequence is skin thinning with longer use. A better choice for fissures is one of the above treatments, but hydrocortisone can still play a useful part for some people if used correctly. The big mistake is when you hear of people who have been using it for months on end.

I was prescribed it too just for two weeks and it definitely helped things.

I guess it can help then if used correctly!
On the note of inflammation, which is part of what it helps with - is a Sentinel Pile considered inflamation? How would the ointment affect that in either case?

the fissure itself will have inflammation, and if the sentinel pile is sore, reddish or swollen feeling, it could help calm some of that pain and swelling down.

I also was given the hydrocortison in my last visit to the doctor, I thought it was for itching, I use it only once and that was all, I better start using it again, after my later flare up due to sickness, my skin tag is a bit swollen.
Still I though cortison was bad for fissures also as it thins the skin.

I also got cortison. I've used it 7 times and didn't feel much improvement. I think Cortison can be good if your condition is a lot worse.. with very big tear to the point that you can't even sit. In that case, you'll need some immediate way to reduce inflammation. My condition wasn't that bad when I saw the GI. I wasn't bleeding at all.