I have never, ever, heard of somebody being denied boarding because of the middle name.
They match last, first is all. Perhaps 10-20% of pax will have issues with middle being mangled in some way.
Now, the online access can be a bit of a pain. If you want to bring up your reservation by name, you might need to try various versions. But that is just a minor annoyance.
Trying to change the ticket is probably difficult, and more likely to lead to a screw-up than just ignoring it.
And I have flown on MU as all of:
exwannabe, joe bob [My passport]
exwannabe, joe b [my CC]
exwannabe, joe mr b [have no clue what this is]