1. A computer-implemented method of diagnosing formatting errors in document renderings, comprising: in a computer system: generating a first rendering of a document, the first rendering corresponding to a first locale; generating a second rendering of the document, the second rendering corresponding to a second locale; identifying a plurality of differences in visual appearance of display characteristics of a plurality of textual elements of the document in the second rendering as compared to visual appearance of display characteristics of a plurality of textual elements of the document in the first rendering, each of the plurality of differences corresponding to one of a plurality of predefined criteria, and the plurality of the textual elements of the document in the second rendering having second formats distinct from first formats of the plurality of the textual elements of the document in the first rendering, wherein the differences comprise potential formatting errors; generating a report specifying at least one of the plurality of the textual elements of the document in the second rendering as having the differences, wherein the report comprises a location descriptor specifying a location within the document of the at least one of the plurality of the textual elements of the document in the second rendering having the differences and flags to indicate whether at least one of the plurality of predefined criteria applies to the at least one of the plurality of the textual elements of the document in the second rendering; and filtering the report using the at least one of the predefined criteria to generate a list of the at least one of the plurality of the textual elements of the document in the second rendering having the differences.