This is another option of the Bad Document Correction Tool (Issue 75524).
The purpose of the option is to remove excessive font variability.

Some users tend to use huge numbers of different font parameters. They seem to
assume, that the more fonts and font variants are used, the nicer and profi" the
document looks.

In fact, every-line-has-its-font documents are awful.

Yes, we can globally change the font. However, we could miss some formatting
behind too.

The OOo should scan the whole document and make statistical analysis, how many
letters are under each font variant. We consider any difference to be a new font
variant, for example italic/bold settings, font size etc.

Then, OOo would choose the 3 (or 4) most represented ("main") variants and
reformat the whole text to use just these. Every part of text, that is under
other font variant, should be applied the "main" font variant that is somehow
closest to originally used one.