Just something minor, but if the capitalisation between online stores (iTunes, Amazon, etc.) or streaming services (Spotify, Deezer, etc.) is different from the cover art, I should follow the capitalisation of the cover art, right?
Actually you should use the MB style guidelines for capitalization.
Cover is King. Followed by polish using the guidelines. Shop adverts are always unreliable.
I only use a shop as reference if there is nothing else left.
Usually the cover art is “most correct” and I try to follow that.
Generally for capitalization (as well as many other style issues) you should always follow the style guide unless you have a good reason to claim artist intent.
Inconsistency is usually a good counter argument for artist intent, but info on online stores are usually not written by the artists or their representatives themselves.
But still - if you only have one album cover you should go with the style guide. If you have album covers for multiple releases and they are all consistent, then go with that.
PS: Maybe I should clarify why I think the answers here differ so much: It all depends.
If e.g. the cover says: “I Want To Love You” I think we’d all agree that that should be changed to “I Want to Love You” - even if there is consistency on different album covers.
If the cover says “I Want to LOVE you” I’m sure we’d all just go with that unless the majority of covers of official releases don’t write “love” in all caps.
So: If the cover simply doesn’t follow the style guide that should be fixed - for words that look like they are written differently on purpose artist intent can be assumed.