I use my seam ripper. Don't have room for another tool on my sewing machine.
I think it would greatly help if you starch your fabric heavily before cutting.
When you're sewing triangles like that you are sewing on the bias and it tends
to get distorted.

there is danger off hitting the seam ripper and a piece of metal flying off as it is only thin--a true stilleto may be stong but a piece of broken needle may fly off--a shortened wooden skewer is more forgiving holds the fabric and may let the needle live on if they connect--my mate worked in E D loved telling me horror sewing stories

I use a double pointed bamboo knitting needle as a stilletto, I also use it a lot when I'm ironing if I want to press open my seams. I have a lovely metal stilletto that someone made me with beads, but I, too, have a fear of metal getting in the way of my needle and something bad happening.

I just use my seam ripper as well as a stiletto. As to hanging on to those triangles...I keep the index finger of my left hand up against the left edge of my foot with the fabric under that hand. Don't have an issue with it wiggling that way.

I use mine all the time also. I also use it when I do the machine side of my bindings. When I get to the corners to make the miter.

All the time

I bought one and seems I lost it right before I could use it. My cats may have had something to do with the disappearing also. It now be in a drawer, hard to keep up with it. I usually sew triangles out of a square and don't need it for that.

Yes. I'm learning to use one. I make them as gifts, but kept forgetting to keep one by the machine. They really come in handy for that last 1/2".

I have a Purple Thang. Had to buy it for a class one time and thought I'm never gonna use this. I seem to go in spurts. Guess it's whatever I'm working on but it will sit for a long time before I think I need it and have to search for it.

I can't sew without it. I have one made by an artisan, out of an acrylic pen blank and turned on a lathe. It fits well in my hand. The business end is not too pointy. I guide the patch thru to where it's going to disappear under the foot. The only time I don't use it is when I do curved piecing and I use a pair of bent tweezers for the last bit.