Just updated to Sierra and updated Pages at the same time. Now when I attempt to select a line of text I end up with an insertion point where I stopped selecting

The ability to select multiple document entities (e.g. words, sentences, paragraphs, etc.) existed in Pages '09 v4.3 by using the command key. This functionality was lost in all releases of Pages v5 and now v6.

Are you using a Wacom tablet by any chance?

Workaround: press the shift-key just before you stop selecting. And yes, this looks like glitch in Sierra.

When using an Apple Magic Mouse II, or external Trackpad I, or the trackpad on my 2014 MacBook Air, text is always selected, and the insertion point is (though hidden), always at the end of the selected text. As has been pointed out in previous posts (for some time), and again here by Esquared, Wacom input devices are incompatible with Pages v5.6.2, and now v6, and may continue at the mercy of Wacom, not Apple.

The above Apple input devices work properly for text selection:

• El Capitan 10.11.6
  • Pages '09 v4.3
  • Pages v5.6.2
• macOS Sierra
  • Pages '09 v4.3
  • Pages v5.5.3 (Documents created, or older v5 documents edited by v5.6 or later, will block and require v6)
  • Pages v6.0

FWIW: up till 5.6.2 Pages was working fine on my MBP with a Wacom tablet. It only stopped working after the 6.0 update. Since that version came with Sierra, it is impossible to tell what has actually caused this.

The problem selecting...a single line, multipliable lines using the shift key, multipliable selected lines using the option key don't work...help...