Spoof touch capabilities such that all Tor Browser users claim to support touch and the maximum number of touch points
dom.w3c_touch_events.enabledin legacy/trac#10286 (moved) as a defense-in-depth against fingerprinting while providing a patch to neuter the risk here as well. The patch got upstreamed in https://bugzilla.mozilla.org/show_bug.cgi?id=1382499 and made it into Firefox 60 ESR.
We should think about whether we should enable the preference again for desktop platforms. We start doing that for Android with legacy/trac#27256 (moved).
Edit: We should go with 'Option B' as outlined in @thorin's post here: #28535 (comment 2848069)