The shard on Gardevoirs' chest can phase through their mates.
Whenever a Gardevoir embraces her mate of choice, her spike will phase through her mate, allowing her to have direct contact with them withought the spike being in the way. The spike is phasing through the mate's body and is amking a direct contact with their heart, which connects their hearts and emotions, in a sense, aloowing them to better feel their emotions and feelings, which drives them to a state of an euphoria.
When two Gardevoirs attempt to embrace each other, their spikes do not phase through, but rather touch each other and glow faintly. The same event as the one described above occurs.