QDoc generates duplicate entries in .index and .tags output files. The same documentation entity can appear multiple times in the generated output, which violates the expectation that each entity is listed exactly once.

This affects the reliability of QDoc's output for tools that consume these files, as they may process the same entity multiple times or encounter inconsistencies in the documentation data.

Expected: Each documented entity appears exactly once in generated output files.
Actual: Some entities appear multiple times in .index and .tags files.