Demonstrates how to retrieve a text object resembling the last text style range *within* a single line.

getLastInlineRange.js

#target indesign

// use on some text frame with several text style ranges in the first line
// if the text range continues into the second line, only the range within the first line will be returned
var l = app.activeDocument.textFrames.firstItem().lines.firstItem();
var lir = getLastInlineRange(l);
app.select(lir);

function getLastInlineRange(l) {
  var ltsr = l.textStyleRanges.lastItem();
  return ltsr.lines.length > 1 ? l.parentTextFrames[0].insertionPoints.itemByRange(ltsr.insertionPoints.firstItem().index, l.insertionPoints.lastItem().index) : ltsr;
}

Regarding the issues discussed in this Tweet.