I can answer that, as I play with the client in French with Japanese voice overs (I tried switching to the English client once, but Ye Olde English and the way the text was even more different to what basic Japanese I could understand were really distracting and I couldn't stand it).
I often speak with people who have played the game in English, and when discussing specific lines, there are way too often instances of "what the hell are you talking about" on both sides. Then I go check into my screenshot folder, unearth the specific line by comparing character poses with the English screenshot provided by my friend, and go "wait… it's this line??". That happens a little too often for my tastes.
Often it's because of the English localisation being weirdly vague and flowery, choosing to go with epithets over bluntly saying things, which sometimes leads to people misinterpreting things and incorporating that into theories that are… well, just plain wrong. FR has much fewer flourishes than EN, the price to pay for sticking closer to the JP script which is usually very straightforward. I know that results in the English script often being more fun and having the most iconic lines, and that is cool I'll give it that, but its vagueness tends to intrude in discussions in a way I really don't care for.
One example I readily remember is of Emet's lines in Ultima Thule. I know someone playing in English who thought some of his comments were praising/referring to the WoL, while the French script makes it obvious Emet is in fact talking about Venat, whether it is by naming her, or thanks to French's much more gendered grammar and the fact that my WoL is male. Amusingly, how omnipresent gender is in French also means I had a "wait… why does everyone act like we don't know Venat is a woman??" moment from 5.2 to the release of 6.0. Apparently her gender wasn't clear in the English version of the Anamnesis recording. Due to how French works, her gender being mentioned in the Scions' lines was inevitable, but there is no reason why English couldn't simply add a mention of "that woman, Venat" or something to that effect.
Another one I can think of happens during the Zodiark trial ("The Dark Inside" VS "Le Cratère des Martyrs" – though given that Japanese trial titles are usually extremely blunt I'm going to guess the original was something to the effect of "Zodiark destruction operation", and that EN vs FR here is simply a matter of their respective localiser bias, which is interesting to see) is Fandaniel going "My life's work! My masterpiece!". In French, he is talking about how long he has waited for this day where he would finally destroy everything. Innocuous enough, yeah? But the thing about this fandom, and how… ugh… bizarrely incensed discussion can get around certain parts of lore, is that some people interpret the English line as evidence the concept of Zodiark was built by Fandaniel himself, and go off that about how essential Hermes was to the Convocation – and I'm not going to go down the Story of Endwalker Sucked rabbit hole because that would be off-topic, but it's just an example that came to mind.
Y'shtola, at some point in 6.0, saying "'Twas Hydaelyn who forestalled the Final Days" is also a "technically true" doozy that can be wildly misinterpreted, while FR has her saying, a lot more explicitly, "by keeping Zodiark alive, she forestalled the return of the Final Days he had originally prevented".
I mean, taken in isolation, all of these are innocuous. But personally, it's a recurring annoyance in my talks with friends, and I've seen it needlessly influence lore discourse when the arguments shouldn't even exist in the first place. Because whatever else English might be, it is the language most used internationally, and thus the EN localisation is the one with the most weight in everyday discussion.