I run into this a good bit where surnames have been changed. In my own family Burk became Burke, Brooke became Brooks and Gibson became Gipson. What would be really handy is that when you type a name into the surname field you had the option of adding more than one. Then you could sort the results by date of birth and see that yes there is a Joseph Burk and a Joseph Burke that are probably the same. Now all you'd have to do is argue with the other profile owner about what it should be. Is this possible?
I don't believe that WikiTree supports Soundex natively however if it did we could simply type in a single name or soundex equivelent. Definition: <!-- Fill in Definition -->A phonetic coding system used to group together surnames that sound alike, but have variant spellings. Every Soundex code consists of a letter (always the first letter of the surname) and three numbers
Example: SMITH/SMYTH/SMYTHE would all have the same soundex code, S530. http://genealogy.about.com/library/glossary/bldef-soundex.htm
with last names there is a field for "Other Last Name(s)" field that could serve that purpose. when it comes to spelling most people tend to use the most current form. for example mine Warren, old style varriant warrin,warren,warryn... list goes on.