I’ve experienced different effect pedals that have feedback at the end of the notes played. I imagine in some amps you can have better feedback than others. My opinion is sometimes you want feedback sometimes you don’t.

We have a very good article explaining how to control feedback at:
https://www.guitarsite.com/newsletters/011001/7.shtml

Feedback is great when you want it and an anoyence when you dont, the feedback you get from semi-accoustic guitars in my experience is a lot different to that of the solid bodied type, it’s easier to get feedback from a semi and harder to control, you can either damp the strings or move away from the amp or turn your vol pot off on your guitar, i have a Gibson 335 dot cherry, and if you want feedback on that it’s easy to get and easy to control, it can give great additional power to your solo’s. Although it’s a proper semi-accoustic it has a solid maple block running through the centre of the guitar, and the a stop tailpeice screwed on to that, in small enclosed rehearsal rooms its not so good because the volume gets inside the body of the guitar and makes the whole thing vibrate, its the hollow areas of this guitar that makes it initialy feedback.
The Les Paul on the other hand has similar pickups, and takes a lot more volume to feedback, it has no hollow area’s (apart from LP custom 70’s models have some chambering to cut down on weight).
At the other end of the scale i have a Rickenbacker 360v64, it has a completey hollow body, no block through the centre, and also single coil pickups, it can feedback at quite low volumes and needs those techniques to keep it in check, its not a great instrument for soloing so i tend to avoid any king of feedback with it. Potted pickups minimise feedback too, they are potted with a resin/wax material to fill all those little cavites around the pickup coil and casing, but you can still get them to feedback nicely, humbuckers feedback less than single coils too. Feedback through a mic is horrible, and most other types is too, but in the right hands and with the right techniques it can be realy musical through a guitar.

TJH, I can only chime in on causes and eliminating. I’ll leave it to proper, real guitarists to post on controlling. That’s a real skill. C’mon in, 6-stringers… 🙂