[dmitrij]

In the last decades philological standards for reproducing the original form of a musical work taking into account historical musical traditions, composing and performance practices have become much more thorough. Editions from the 19th and early 20th century which you can find on IMSLP because they are out of copyright restrictions often don't meet these scholarly standards. They very often reflect performance practises and the style of their time. See also https://en.wikipedia.org/wiki/Urtext_edition.

[perihelions]

But – there are tons of prestigious, high-quality, Urtext editions on IMSLP, because

https://imslp.org/wiki/IMSLP:Copyright_Made_Simple#Urtext_Ed...

(copyright laws afford Urtext editions shorter terms of protection than original works)

[wuiheerfoj]

I’d add that some of the older texts are really badly laid out - often handwritten or in a strange typeface that makes them really hard to mentally parse when you‘re used to the uniformity of modern scores.

That said imslp is still a life-saver and playing music would be a lot more painful (and expensive!) without it

[mavhc]

Is there a standard file format for scores? I see MusicXML and MEI.