<p>You are correct its in Scintilla which seems to coalesce continuous sequences of typing and deleting.  So if you type a whole paragraph without taking breath it will be treated as one "thing".</p>
<p>The problem with "common linguistic delimiter" is its filetype and (human) language dependent.</p>
<p>Scintilla provides a means to get greater control, so since Geany does very little control of undo redo plugins could provide human/programming language specific redo control.</p>

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