I kept having failing palm rejections on my new 2018 MBP's trackpad. I've never had any issue on my 2013 MBP or my 2009 MBP trackpad. The 2018 MBP's trackpad is impractically huge, and the heel or base of my thumb would register a false click while I'm typing or changing in between typing and trackpad use.
I had to enable dragging (without drag lock) since I'm so used to tap-to-click and that exacerbate the issue bad enough that I can't even complete typing any email without repositioning the cursor, or worst, undo-ing jobs manually because the trackpad falsely double-register a tab selection and delete someinsert/delete lines as I type, especially while I'm typing or coding really fast.
What makes it worst is also the trackpad is slightly off centered to the right making the right thumb base more prone to false registering as a finger.
I tried a few suggestions found on google and played with the sensitivity but none really helps. I resort to cover the side of trackpad (plastic-foil-plastic layer) to block it off. It's not a perfect solution but at least it takes care of most (~90%) of false registering. But that also means I cannot swipe from edge to bring up notification center. Plus it looks clumsy after spending that much money on a MBP.
Having been using MBP most of my life I'm sure I'm not the only person having this issues with 2018 MBP - is there a better or preferred (software) solution to improve the palm rejection?