It's generally agreed that \center-align is confusingly named; users
expect it to be related to \left- and \right-align when in fact it
centres a column of text.
As a solution, I present Mats's proposals for renaming:
Proposal 1:
Use
left-align, center-align and right-align
for the horizontal alignment of a single markup and
column, centered-column
(or left-column, center-column, right-column)
for vertically stacked markups.
Proposal 2:
Use hleft, hcenter and hright for the horizontal alignment of a single
markup
Use left-align, center-align, right-align for vertically stacked markups
I favour the first option (using \center-column), since it keeps to a
minimum the number of syntax changes.