Comment 2 for bug 1585897

I doubt this is easily fixable (or fixable at all) - the extension script has no access to the precise position of individual words and characters within laid-out (rendered) text - these details depend on SVG style properties in effect for the individual tspan/text element, the font itself (including style variant, size), and may even differ depending on the font backend (platform-specific) and font backend configuration (e.g. fontconfig, fallback fonts) of any SVG renderer used to render the SVG. IIRC this known limitation was already discussed on the devel mailing list at the time the extension was originally contributed several years ago [1], and I'd be surprised if there aren't already older reports about this lack of feature.

[1] https://sourceforge.net/p/inkscape/mailman/message/22164016/