You are being a little disingenious at this point.
Your original assertion was:
"Having multiple names in the Middle Name field is not appropriate for Wikitree. " Which is patently false.
You're now trying to qualify it by saying that the use of "or" is the problem.
Why did you not say that in the first place...
And what other words would you like to disallow as not "appropriate" in the middle name?
Here's something for you to think about.
Just because a WT report says something is "wrong" doesn't mean it is wrong.
I'm regularly plagued by "data doctors" who don't think, because a report tells them so, that "Major" is an acceptable middle name. It "must be", so I'm told, a prefix.
Except, of course, if you were one of the many:
first name - Major as a middle name - surname people in the area I know about.
Data doctors blindly following reports and insisting they know best do not do WT any favours.