Edit: where did you get the PDF? I don't see any on the official Gimp site.
Likely not a font, but an uncontrolled "typographic replacement". Many word processors replace the "simplistic" ASCII single and double quote from our keyboards by the "typographically correct" apostrophe or opening/closing double quotes(*). But computing languages want the true ASCII characters, so when you copy/paste from a document you take your chances
By the way if you want to write Gimp scripts in a modern and understandable language you can do so in Python.
(*) My personal favorite was a "ZERO WIDTH NON-BREAKING SPACE" inserted in a file name by the author to make sure that MS-Word would not hyphenate the filename. So he replaced a visible alteration by a much less visible one. Two days of downtime while the operation folks figured that out, which required counting the bytes in the file name and discovering that there were a couple too many.
Likely not a font, but an uncontrolled "typographic replacement". Many word processors replace the "simplistic" ASCII single and double quote from our keyboards by the "typographically correct" apostrophe or opening/closing double quotes(*). But computing languages want the true ASCII characters, so when you copy/paste from a document you take your chances
By the way if you want to write Gimp scripts in a modern and understandable language you can do so in Python.
(*) My personal favorite was a "ZERO WIDTH NON-BREAKING SPACE" inserted in a file name by the author to make sure that MS-Word would not hyphenate the filename. So he replaced a visible alteration by a much less visible one. Two days of downtime while the operation folks figured that out, which required counting the bytes in the file name and discovering that there were a couple too many.