I also have many positive things to say about Standard Ebooks, but I don't think you were asking about those. :)
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Edit: Without going into what I think are the most egregious sort of changes they introduce (which I think will require a longer post) and limiting myself to ones easy to find immediately:
See the earlier discussion (linked in a sibling comment here) where the editor-in-chief says it's ok to change punctuation because "The sounds out of his mouth do not include an apostrophe whether it's there in the spelling or not." (a very American view IMO): https://news.ycombinator.com/item?id=16956931
And looking at a recent commit on one of their books, here's a recent (https://github.com/standardebooks/agatha-christie_the-secret...) revert of one of their aggressive "modernizations" from 2024 (https://github.com/standardebooks/agatha-christie_the-secret...), that had, in line with their usual practice, changed "every one" to "everyone" (in one place even when referring to "a good many risks"), and the same commit made other changes (including one still present) like "they ought to have it lithographed. It must be a frightful nuisance doing every one separately." having the last four words turned into "doing everyone separately."!