Recently me and my colleagues using SharePoint have run into some
difficulty with certain list columns. We found that columns such as
Title cannot be altered or deleted in lists. This has even occured
when publishing a list from Excel. In our example, the leftmost
column, a column of text, was converted into a multiple-line text
column and was unchangeable. This made if impossible to group the
results by this column in the list. I am guessing it took that text
column and turned it into a Title since there was no explicit "Title"
column in the Excel list. We ended up deleting and recreating the
column but we'd like to know how the program determined to lock this
column in the first place.

I'd like to know how are the locked columns determined and why? Is
it strictly a set of columns that SharePoint has deemed off-limits to
users? If so, what are the "locked" columns? And in the case of
Excel importing, is there any strategy to properly import lists
without any surprises like that?