Most people are familiar with Murphy's Law ("Anything that can go wrong, will") but those of us who try to write publicly about language are susceptible to Muphry's Law, the rule that if you write something where you criticize someone's grammar or editing, you will make a mistake yourself in the process. (Heck, I almost misspelled "law" as I was trying to type in that last sentence.)
Because I'm not trying to be the Authority on Grammar here, I hope that I'm not setting myself up for numerous instances of Muphry's Law In Action here on "Please Stop Confusing My ESL Students." I'm sure that I'll make my own mistakes, and I just hope that I'll catch them before too many people see them.
Around ten years ago, I used to work as a volunteer teacher on The Help Center at Dave's ESL Cafe and I know I made some mistakes there from time to time, including once using "There's many..." instead of "There are many..." I sometimes joke that the best way to learn a particular grammar point is to make a big humiliating mistake with it.