1. Create a new Writer document. 2. Type two paragraphs (say, "aaa" as first paragraph, "bbb" as second one). 3. Apply a distinct style to the first paragraph (say, Heading, or Preformatted text). 4. Enable change tracking. 5. Put cursor to the start of the first paragraph, and select to the start of the second paragraph. 6. Press Del key, so that the whole first paragraph is marked deleted. 7. Inspect, that the first (deleted) paragraph still has the style ald look assigned on step 3. 8. Save as ODT. => already after this step, even without any reloading, the style and look of the paragraph 1 (marked for removal) changes to the default style.
The behavior inherited from OOo was, that on step 8, the style of paragraph 2 was changed to the one of paragraph 1 instead. In 6.2, step 6 changed the style of paragraph 1 to the one of paragraph 2. In 6.4, it started to work as shown in comment 0. So this is kind of inherited from OOo, but the wrong behavior changed twice; and those changes of behavior may potentially serve as code pointers.
I tried in 6.4 with saving DOCX where bug is not seen to ODT, but got wrong: commit eeb9481304572cc404ea1da9f3dabff43d6d191c [log] author László Németh <nemeth@numbertext.org> Fri Jun 14 17:02:20 2019 +0200 committer László Németh <nemeth@numbertext.org> Mon Jun 17 09:30:00 2019 tdf#125916 DOCX import: fix outline numbering at tracked deletion Change in 6.4 is: commit 1aac73a1fb260e4c76a483a68f003913fdd2c4bb [log] author László Németh <nemeth@numbertext.org> Thu Jul 25 14:58:23 2019 +0200 committer László Németh <nemeth@numbertext.org> Thu Aug 01 09:43:27 2019 tdf#125990 change tracking: remove text join workaround