Hello! That sound is a combination of a Digitech Whammy WH5 and a BOSS DD5. To clarify, the particular performance is Paranoid Android at Coachella 2017.
Ed’s pedalboard for Radiohead’s 2016 tour, from one of their 2016 performances in Paris (danielthegigrig). The Whammy V and DD5 are both on the main pedalboard (the one on the left).
The Whammy V is set for an single octave shift, enabling Ed to play the his high guitar part during both of the “What’s that?” sections. Ed originally used a Digitech Whammy II to play the part on OK Computer, and used a Whammy IV for many years before switching to the V.
Though low quality, this picture of Ed’s pedalboard for Radiohead’s 1997 tour shows both his Digitech Whammy II (on the left board) and BOSS DD5 (on the right board).
The delay sound is clean, and the repeats don’t darken, making Ed’s DD5 the most likely candidate. The feedback on the DD5 is set to max, meaning the delay will repeat infinitely (the DD5 doesn’t oscillate), which is why the delay never gets quieter. When Ed bypasses the DD5 at 2:08, it cuts out immediately – we don’t hear any trails. This means that Ed bypassed it via his TheGigRig G2. After bypassing the pedal, Ed leans down at 2:14 to adjust the DD5 for a non-infinite setting with a much shorter delay time. The new setting used on this particular performance has more repeats than that heard on the album recording of Paranoid Android (on which he almost certainly used a DD5), probably to compensate for extra layers of instruments which are by necessity absent in performance.
Ed adjusting his BOSS DD-5 at the start of Exit Music (for a film) in Lyon, 2016.06.01 (youtube).
It’s worth noting that the “trails” on the DD5 are a bit different than on most delays. When the pedal is bypassed, it quickly fades out the delay sound regardless of where the feedback knob is set. As such, you can get some brief trails even when its set for infinite feedback. Compare this to the BOSS DD7, which will continue to repeat forever if it’s bypassed when set for infinite feedback, or a BOSS RE20, which will can be used as an oscillating sound source even when bypassed (so long as you feed it a little signal before bypassing it).