Issue: Apostrophe symbol has been replaced with unknown symbol

Today for the first time we started to compare article content with the software beyondCompare and it turns out that the number of issues is immense. Please try this with the same article as referred to in this report. It has 110 lines with differences.

Without checking out every instance of characters that were not imported correctly, we so far found that the following was not imported:

Apostrophe, "(quotes), tree dots, € (euro), – (minus), α, ä, α, δ, anything greek, arabic, Chinese, Persian.
Basically any symbol and any character that is not basic latin.

There must be some way that the importer can insert the old text into VW4/XF in the same way that the stock xenforo importers insert the vbulletin content into xenforo. We do not encounter the same issues there. Similarly we imported 26k articles & blogs from vbulletin threads into AMS and 10k journals from vbulletin threads into UBS without this issue. I know for sure that members have been using the same characters there and have also employed MS Word to write those articles.
I dont know if it is a useful remark, but maybe the same concept can be implemented?

It looks like all or almost all wiki articles are affected by this issue.

The method that is employed by all those importers does not work with 100% of cases, because vBulletin allowed multiple languages with different character sets and encodings. Our importer used to do it the same way as the others and it created similar issues on some sites. The most recent system in VaultWiki worked with nearly 100% of cases, but due to a bug you reported in 4.0.16, we had to change it because MySQL strict mode was not accepting some characters. The change for MySQL strict mode, which prevents bytes that MySQL strict mode complains about, appears to also remove unintended bytes from some characters.

This was resolved by one of the fixes to the issues you linked as possibly related, most likely the one where I discussed Windows-1252 detection. Marking this as a Duplicate.