Oh, I wasn't aware of this fix! Thanks for posting the solution Wes.
I generally avoided using sticky keys in Moho because I thought the lag was normal when a Moho project reached a certain complexity or number of keyframes.
Will check my Repeat Rate to see how it makes a difference for a heavy project file, and then try the script to fix it specifically for Moho.
I checked my Repeat Rate and Repeat Delay setting and they were already set to the fastest/shortest settings.
For me the lag occurs most noticeably when the Style window is left open (as Wes noted,) even with a fairly simple project file. It's really bad with a more complicated project. When I close the Style window, Sticky Keys is reasonably speedy. Leaving the Tools or Switch Selection window open has a minimal lag effect...it's there but barely noticeable compared to when the Style window is open.
I guess this is fine for me because I normally keep my Style window closed during animation, but knowing specifically what causes the lag is very helpful!
Hopefully this lag with the Style window open gets properly fixed in a future update.