I removed it once. I may be mistaken here, but if I recall, removing it slightly shifted the layout of the other keys throwing off my muscle memory for the f keys.

I'm interested in a solution. I probably hit that key unintentionally 10 times a day.

Check out this post about customizing the touchbar that was on HN a little while ago: http://vas3k.com/blog/touchbar/

Perhaps you could replace the Siri button with a similar sized button if one is available, in order to keep the spacing. (I don't have a touchbar Macbook, so I don't really know what's available.)