Tool-tips need to be enabled with <F3 + H>

Mobs to summon:

/summon Villager ~ ~1 ~

/summon Villager ~ ~1 ~ {CustomName:"Test"}

Then type the following into the chat:

/say @e[type=Villager]

Hovering over an entity in the chat will display basic information concerning the entity. However, if the villager is named, no tooltip shows up.

See the attached image (v1). The tooltip will show up when hovering over the villager you have not provided a name for, but will not show up if you named it using the 'CustomName' tag.

This does not occur with other entities. For example:

/summon Creeper ~ ~1 ~ {CustomName:"Creep"}

/say @e[type=Creeper]

The next attached image (v2) displays the named creeper having the proper tooltip.

Unsure if this occurs with other entities besides villagers.