There's a scene in Thor: The Dark World which it is forgivable if you've forgotten about. It's one of those expository scenes where Odin tells Thor and the audience basic historical plot points and such. Here he explains to Thor what Malekith's plan is, cluing him in to the power of the Æther.
When the Easter eggs for the Marvel movies are talked about, this scene is mentioned. It's the scene where we are given the implication that the Æther is an Infinity Stone (confirmation comes during the Collector scene).
What gets lost in the shuffle is this fine image I procured by putting on my digital copy of the movie, pausing it to show as much of the golden runed glory of the page as possible. It's beautiful, but what does it mean?
To my surprise, I cannot find anything online which addresses what these runes mean. Fortunately for us, they're still writing in English. Here's what the runes say:
The elves fought against the light that radiated from Asgard. They built a weapon out of the dark and unleashed the dark power of the æther acros (sic) the nine realms, inflicting the torment of [...]
It's interesting to me on many levels that the runes here are essentially English. Even more interesting is the choice of runes. These runes are the runes of the Elder Futhark, the runic alphabet which gave birth to both the Anglo-Saxon runes (the first alphabet of English) and the Younger Futhark (which the Vikings used). The Elder Futhark predates the Vikings, being the alphabet for the runic language of the early Germanic tribes.
So it makes sense that the runes are Elder Futhark here. The Asgardians are the beings worshiped by the early Germanic people, so it's no surprise that Asgardian writing would come to Midgard.
The weird thing, as I said, is that the runes just spell it out in English. These runes are ancient; they should be written in Old Norse at least (Proto-Germanic would be ideal, but it's too poorly attested to be done properly, so Old Norse would be the best option despite still being anachronistic). Do Old English if you can't do Old Norse. Or Middle English. Or even that fakey Olde Englishe spoken at Renaissance festivals which has about fuck all to do with how English was ever spoken except in the imaginations of Victorian poets trying to create a medieval feel. Anything but modern standard English. Film and television are no strangers to this, though.
The television show Vikings featured this attempt at runes in its season two finale:
That, for those who don't read Anglo-Saxon runes, says "Shord of Cings" - a transcription error-laden in several ways. To make the sound "Sh" Old English used "Sc", the "ng" sound had a single rune, and if that weren't enough they wound up spelling "shard" wrong even if the goal was to simply spell the modern word in runes. A real Old English sword wanting to say what this sword tries to say would read, transliterated, "Cyninga sceard" (noting that the "ng" and "ea" combinations would have their own runes, not to get into the issue of dialectical variation between the West Saxon I use here and the more likely Northumbrian dialect that runes would employ).
The Thor runes, if transcribing Old Norse instead, would look something like this:
Alfarnir slógust við ljosinum það frá ásgarði geisluðu. Þeir byggðu vápn úr myrkrið ok gáfu myrkraptinum ljósvaka lausann tauminn yfir níu ríkin, orsakandi kvölina af [...]
(This is a rough translation into Icelandic and then archaized by using Old Norse forms where I could find them and how they differed from modern Icelandic)
This would be more accurate (though still anachronistic, so "more" accurate is an extremely relative concept), but we do ultimately have to think about film and television, how and where it's produced, and who sees it. Most movies and shows involving runes will, ultimately, come from Western studios. It's in or adjacent to our cultural background. Correspondingly, the biggest consumers of film and television featuring runes and Nordic culture will largely be Western audiences, which the Anglosphere dominates.
Ultimately, it comes down to an attempt to render something the audience might be able to understand. A string of runes spelling out something in Old Norse or modern Icelandic would, to much of the audience, read as complete gibberish even if transliterated. In an unfamiliar language without spaces, it can be nearly impossible to determine what even are words. Even with a familiar language that can be hard.
Hard, isn't it?
So putting the unfamiliar letters over modern English becomes their way of throwing a bone to viewers. When done wrong, like in the Vikings example, it's almost comical. You could speculate that perhaps the runes on that sword were put there by a Northman who had only passing familiarity with inscribing English and just did his best. But on a fundamental level, it shows that the writers didn't try, or didn't lean on their Anglo-Saxonist consult enough (if you're reading this, History Channel, call me if you're hiring).
When done right, we get something pretty beautiful. The runes in Thor are nearly perfect, the only problem being the misspelling of "across" by shorting it a letter. This is not due to a desire to prevent doubling of like runes (the first two words do it right away), but is probably due to space limitations. The page only has six lines, and adding that second s would mean removing the final f from the last word. "Across" is understandable if it loses its final letter; "of" becomes an open-ended cipher. Whoever Marvel hired for runic consult did a pretty good job, all told.
Maybe that person can tell the rest of us how to get such a sweet gig out of our English degrees.