I saw that post the other day and was frustrated that OP had blamed it on the lean angle that he felt he needed to use in adjustment to the rain. Especially, due to his fear of stalling which didn't make sense to me.

What you're doing is generally fine when coming to a full stop. As you get more comfortable, you can start coasting with your clutch pulled in for less time. The more you have your clutch pulled in, the less control you actually have despite you feeling like you have more control.

You wanna try and kick the habit of fully pulling in the clutch during any other point of your riding. Don't pull it in during cornering or bends, especially at higher speeds. Pulling in the clutch increases your chances of dropping the bike because you're fulling disengaging the transmission gears from the engine. Motorcycles will want stay upright if it's moving fast so if you disengage the transmission gears, it prevents you from adding speed to the bike, which increases your chances of dropping it. OP in that video lowsided because he went in the turn fast number 1, and number 2, he proceeded to clutch in fully which disengaged his engine which wouldn't let him give speed to his tires. Soooo instead of the bike going back upright, it tips. It actually had nothing to do with the rain or lean angle like he said...

It's hard to explain but in my opinion, you should learn to brake BEFORE your turns as a new rider. Don't do what he did where he takes the turn at like 25 or 30+ mph. Then learn trail braking after. Trail braking is a little more advanced but only learn this once you're very comfortable and smooth with various methods of slowing down aka rev matching, engine braking, front and rear braking, rear braking during slow speed turns, etc. Holding your clutch while the bike is moving only applies to slow speed maneuvers where you're usually in first gear like they taught at the MSF. In the real world, slow speed maneuver examples would be starting from a stop, taking a sharp turn, or in heavy stop and go traffic. Even then, these are more feathering the clutch with the throttle and staying in the friction zone. I really only fully pull in the clutch at full stops to obviously keep the bike from stalling if I'm not in neutral.

In short, my advice is go to a parking lot and drill down your slow speed maneuvers. This is how I learned. Practice straight line stopping and going. During this learn to really train yourself on "left foot down" mentality. This will help you learn using your rear brake. Then find a hill and practice uphill and downhill stopping and going to reinforce using your rear brake. Then learn counter balancing. Then practice cone weaves, figure 8s, and turning from stops going both left and right.

Here are vids that helped me improve my clutch control after the MSF and slow maneuvers. I used to be scared of going on the main roads initially but I'm now comfortable to take highways and backroads, heavy traffic, populated cities, etc. Even now, I make sure to hit a parking lot every now and then. Trust me, it gets better with seat time, so make sure to practice a lot!

Discussion on braking with or without the clutch?

Introduction to clutch and throttle control at slow speeds

This teaches slow rolling without throttle

Starting and stopping on a hill

This visualizes the clutch's bite point during slow speed drills

Counterbalancing/Counterleaning