Sentence selection sometimes picks wrong start

Shift+Ctrl+6 finds the start of a sentence by scanning backward for period, exclamation or question mark, but this fails when

  • it is the first sentence in a document. The scan fails and the selected sentence starts at the cursor.
  • it is the first sentence in a paragraph. The scan picks up the previous paragraph separator. It can consume an entire subhead, e.g. for lastword period pilcrow my-subhead pilcrow The sentence I want to select period, it picks up pilcrow my-subhead pilcrow The sentence I want to select period
    The fix is to include start-of-document and start-of-para in the checking.
    If the preceding sentence is a quotation, it will also pick up the closing quotation mark, but that’s a much tougher problem to nail because of quotation marks within sentences. I can live with this quirk.
    P.S. I would LOVE to be able to select a sentence by mouse-click. LibreOffice selects a sentence with triple-click and para with quadruple-click, but I know a late change like this would disrupt your UI :cry:

I can confirm the behaviour in both the cases cited by the OP.

(But the select sentence shortcut is Ctrl+Shift+F6. Ctrl+Shift+6 activates the capitalize command if the 6 key includes the ^ sign.)