Touchpad triggers right-click when touched/pressed with one finger only (XPS 13)

In certain conditions the touchpad triggers a right-click event even though you use *one* finger only. This behavior is difficult to reproduce, but it happens relatively often during regular use of the notebook (a couple of times a day, across various applications).

Seen on a 2015 Dell XPS 13 9343 Developer Edition running Ubuntu 14.04.3 LTS with 'Tap to click' disabled (via System Settings > Mouse & Touchpad).

Suspect / Guess
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Maybe the hardware or the driver detects a certain position of the finger as "two fingers", or there is some other influence on the device (palm close to the touchpad area?) that needs to be filtered out.

Expected Behavior / User Story
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The touchpad works fine with:
- 1-finger touch/click (anywhere on the touchpad) = left-click event
- 2-finger touch/click (anywhere on the touchpad) = right-click event

As a computer user
I want to be able to issue a left-click anywhere on the touchpad using only one finger and issue a right-click anywhere on the touchpad using two fingers
so that I don't have to move my right hand too much (for the left-click) to avoid accidentally issuing a right-click and hence using the touchpad is a more pleasant experience (similar to the MacBook).

How to Reproduce
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Summary:
- Use the XPS 13 9343 Developer Edition (Ubuntu 14.04.3 LTS) normally, and wait for the behavior to happen.

Steps:
1. Disable 'Tap to click' (via System Settings > Mouse & Touchpad). [optional]
2. Work with the XPS 13 using the notebook's keyboard and touchpad
3. Watch out for situations when a context menu pops up unexpectedly (right-click!) when you expected a left-click event (using one finger only)
4. As soon as this behavior happens you'll be able to reproduced it a couple of times (continuing to click the same way)

Comments:
- This behavior can reliably be reproduced by pressing/clicking with one finger on the *right lower edge* of the touchpad. This reveals the (right-click) context menu anywhere, on the desktop and in any application.