How much of methylcellulose is safe? Not a duplicate of this question, as I know that it's used for cooking, I just don't know how much of it is safe.

I heard that methylcellulose is used as a laxative (it is not digestible, just like regular cellulose), and I heard it has other side effects that caused the food industry to limit its use. I'm concerned that too much of it may cause diarrhea. I believe some small amount should still be safe, otherwise it wouldn't be used at all. The question is: how much? And does safety depend on methylcellulose/total food mass proportion, or does it depend on the amount of methylcellulose alone? Any personal experiences?
There is no safe number determined. 

The position of the FDA is 


  There is no evidence in the available information on methyl cellulose that demonstrates, or suggests reasonable grounds to suspect, a hazard to the public when it is used at levels that are now current and in the manner now practiced. However, it is not possible to determine, without additional data, whether a significant increase in consumption would constitute a dietary hazard. 


(from SCOGS)

So, all you can do is to follow recipes and hope that they constitute "levels that are now current and in the manner practiced".