Ttyjfyk

I just moved over to Antergos (Arch-based) from Ubuntu with XFCE and Awesome WM. I use a HP laptop with a touchpad.

When I hold down the left mouse button to highlight text or drag an icon, the drag or highlight action continues for a short amount of time after I release the left button.

(More annoying, the amount of time this "phantom left button" persists seems to be proportional to how long I held it. If I held down the left button for several seconds, it continues selecting text or dragging for 2-3 seconds after that. If I do a very short click and release, the "phantom button" effect is barely noticeable. This behavior has me convinced that this is supposed to be some kind of feature?)

I do not know what this feature is called, making it difficult to Google my problem. It's also the first time I've encountered it.

This is my 70-synaptics.conf:

~ $ cat /etc/X11/xorg.conf.d/70-synaptics.conf
Section "InputClass"
 Identifier "touchpad catchall"
 Driver "synaptics"
 MatchIsTouchpad "on"
 MatchDevicePath "/dev/input/event*"
 Option "TapButton1" "1"
 Option "TapButton2" "2"
 Option "TapButton3" "3"
 Option "LockedDragTimeout" "0"
 Option "MaxTapTime" "0"
 Option "TapAndDragGesture" "0"
EndSection

This is my synclient -l:

~ $ synclient -l
Parameter settings:
 LeftEdge = 1661
 RightEdge = 5367
 TopEdge = 1412
 BottomEdge = 4510
 FingerLow = 25
 FingerHigh = 30
 MaxTapTime = 0
 MaxTapMove = 247
 MaxDoubleTapTime = 180
 SingleTapTimeout = 0
 ClickTime = 0
 EmulateMidButtonTime = 75
 EmulateTwoFingerMinZ = 282
 EmulateTwoFingerMinW = 7
 VertScrollDelta = 112
 HorizScrollDelta = 112
 VertEdgeScroll = 0
 HorizEdgeScroll = 0
 CornerCoasting = 0
 VertTwoFingerScroll = 1
 HorizTwoFingerScroll = 0
 MinSpeed = 1
 MaxSpeed = 1.75
 AccelFactor = 0.0356189
 TouchpadOff = 0
 LockedDrags = 0
 LockedDragTimeout = 0
 RTCornerButton = 0
 RBCornerButton = 0
 LTCornerButton = 0
 LBCornerButton = 0
 TapButton1 = 1
 TapButton2 = 2
 TapButton3 = 3
 ClickFinger1 = 1
 ClickFinger2 = 1
 ClickFinger3 = 1
 CircularScrolling = 0
 CircScrollDelta = 0.1
 CircScrollTrigger = 0
 CircularPad = 0
 PalmDetect = 0
 PalmMinWidth = 10
 PalmMinZ = 200
 CoastingSpeed = 20
 CoastingFriction = 50
 PressureMotionMinZ = 30
 PressureMotionMaxZ = 160
 PressureMotionMinFactor = 1
 PressureMotionMaxFactor = 1
 GrabEventDevice = 0
 TapAndDragGesture = 0
 AreaLeftEdge = 0
 AreaRightEdge = 0
 AreaTopEdge = 0
 AreaBottomEdge = 0
 HorizHysteresis = 28
 VertHysteresis = 28
 ClickPad = 0

From Synaptics man page

Option "ClickTime" "integer"

The duration of the mouse click generated by tapping. Property: "Synaptics Tap Durations"

I guess here is the problem since your config has 100 in the value, maybe you should set it to 10 or even 1?

PS. try with every option that has the Synaptics Tap Durations label in the man page, if the first one is not the problem I'm pretty sure that one of the other 4 should be