Its glyphs were put in visual order and then cut where the path ran out, which kept the text's end. Now the longest start of the text, in reading order, whose glyphs fit in visual order is laid out, as area type does with each line it breaks, by the same rules that place the line: steps where the glyphs sit, hanging punctuation and the path beyond the brackets.
Illustrator links type in an area or along a path (https://helpx.adobe.com/illustrator/using/manage-text-area.html); until now only area type threaded here. Type on a path that overflows ends its line where its text stops fitting, so a story flows on from it, and its red out port, just past its end bracket, loads the Selection tool with the text as area type's does. A new frame threaded from it at a point is type on a path of its shape.
Document symbols placed inline in a run of type (beyond Illustrator; like
InDesign inline anchored objects): TextRun.inline holds the symbol, scale and
shift; the run is one U+FFFC laid out as a glyph sized to the art, centred on
the cap height. text.insertInline and Type > Insert Inline Symbol; editing
keeps the graphic whole; canvas, SVG (<use>) and PDF draw the art; Create
Outlines turns it into a symbol instance.
Each paragraph has its own alignment, indents, spacing, hyphenation, tab
stops and paragraph style (TextObject.paras; para stays paragraph 0's, so
old files and readers work). Layout, editing (split/merge), threads, the
Paragraph/Tabs/Paragraph Styles panels, ranged text.setStyle/setFormat/
tabs/paraStyle.apply, SVG export/import and the fuzzers follow.
Jürg Lehni