Highlight multi-line comments permanently in non-pointer/touch devices

Problem

We currently highlight the multi-lines spanned by a comment on hover in the changes tab. After #217689 (closed) is addressed, it will also work in the Overview tab.

However, if accessed via a device without a pointer, namely mobile phones and tablets or any other touch device without a mouse, the hover will not be possible... hence losing the visual cue of what lines the comment spans.

Proposal

It would be a good improvement to detect this and highlight the lines permanently.

Note: do not assume that a device with touchevents don't have a pointer. MS Surfaces, for example, can have both a pointer AND touch support.

Ideas to properly detect this scenario are welcome.

Screenshot

As can be seen on a tweet by @thomasboni