No, you are not too big to ride. A horse can comfortably carry roughly 20% of its body weight, so if the horse weighs 1200 lbs (average amount), then it can carry a 240 lb rider. This fact has been disputed, and everyone has their different opinion, but I think it's pretty solid.

I weigh slightly more than you, and I ride at least five times a week. I ride a stocky Morgan horse, and a Belgian cross. Both these boys can carry my weight comfortably, and I've never had many issues.

That being said, I'm not promoting it. I do definitely have times where I think I'm too big for my horse. I'm sure there's tons of mean people on this site who think I'm nothing more than a fat slob. I wouldn't ride a thoroughbred, or another lighter-boned breed. I also don't jump higher than cross-rails, though this is partially because I'm not a fan of riding. I also stretch out the horse I'm riding, and I have a half-pad which is designed to help a horse's back. I'm currently dieting, but I'm not willing to give up riding despite my weight.

So go for it! It might be nice to give them a heads up that you are heavier, just so they can get a bigger-boned lesson horse instead of a thin-boned one. At the same time, if they pull out a short horse but one that's "stocky", don't be afraid. I was always told that short-backed stocky horses (Quarter Horses, Morgans, Arabians) can carry more than a large warmblood!

There will be difficulties in being a larger rider. I get out of breath faster. My back hurts when I have to do two point. I'm not as flexible. But riding is helping me improve in all those areas. It's great exercise. Also, since you rode before you'll probably remember the basics, like posting trot, even if they are rusty. A 190 lbs rider who can rise and sit softly in the centre of the saddle will do a lot less damage than a 140 lbs rider who is slamming on the horse's back each rise.

So no, you are not too big for riding. Don't listen to people on reddit who probably know very little about horses. If you saw it in an Askreddit thread that no one over 150 lbs should ride it might have been during the whole "fat hate" thing that was going on. Also, it's a general consensus that reddit hates horseback riders (for the most part). There's no glory in being overweight, but it also doesn't demonize you and prevent you from doing the things you love.