Steven Moffat Bill being gay only comes up when it’s relevant.

The Pilot For instance, when she randomly tells a story about a crush, seconds into the episode.

The Pilot When someone makes a remark about guys.

The Pilot When a love story starts to develop.

The Pilot ...oh, that's ALSO this week's plot.

The Pilot ...AND the resolution of the episode.

The Pilot Travelling with the Doctor, she might meet Heather again.

Steven Moffat Like I said, only when it's relevant.