Clarify the "if your instance previously upgraded from 1.4 to 1.5" statement to only apply to recent upgrades (e.g. the 1.4->1.6 path). That may be confusing for people who have been on 1.5 for some time. Maybe something like "For those attempting to upgrade to 1.6 from 1.4 through 1.5, ..."? That seems a bit wordy too.
If they upgraded from 1.4 to 1.5 with an offline table that has walog entries, that all happened to be the only things on tablet server that was off (or that ran into problems attempting to do the copy, it won't matter how long ago it was. Presuming they ever bring the table back online.
I could maybe explain that the 1.4 to 1.5 upgrade process asynchronously handled migrating 1.4 write ahead logs and that 1.6 can no longer make retries?
In the last paragraph, quote "metadata" to be clear that we're referring to the table named "metadata" and not "table metadata".
I did mean "table metadata". We write into multiple tables as a part of the upgrade, not just into the reserved metadata table. (the new reserved root, for example)