The French are officially "encouraged" to use the "new spelling" of the reforms of 1990 (but the old forms are still allowed). The new spelling is now taught in schools for example and is included in style guides for various media groups. However your algorithm always seems to correct "plait" to the ancient spelling of "plaît", insisting on the unnecessary circumflex. I'm used to it now, as I have been corrected a number of times in various exercises like this one, but surely this must confuse some of your other subscribers? (In my opinion you should probably mark us correct for both options, but if only one is preferred then maybe it could be the new official spelling?)
P.S. Since writing this, I have found some conjugation guides give : Je plais, tu plais, il plaît, nous plaisons, vous plaisez and ils plaisent. With the circumflex included only in the 3rd person singular (which is the only case where it is followed by a "t"), but I have been unable to find a reason for this, or even whether it is correct?