The comprehend languages spell says:
For the duration, you understand the literal meaning of any spoken
language that you hear. You also understand any written language that
you see, but you must be touching the surface on which the words are
written. It takes about 1 minute to read one page of text.
A wizard who casts find familiar can see through the familiar's eyes and gets the "senses" of the familiar as well. Does that mean touching a written language through a Familiar counts as "you" (i.e. the wizard) touching the surface?
Best Answer
You are asking two questions; however, I will address both.
First, the functioning of find familiar's sense-sharing action must be addressed.
These "special senses" include senses such as darkvision and tremorsense (Basic Rules for Dungeon Masters, section Monsters -> Statistics -> Senses). This does not mean the caster feels what the Familiar feels, nor does the caster touch what the Familiar touches.
Does touching a written language through a Familiar count as the caster touching the surface?
No. As stated above, nowhere in find familiar does the spell say that the caster counts as touching the objects touched by the Familiar when sharing its senses.
Additionally, since comprehend languages is a spell of range "self" rather than "touch," the Familiar cannot cast comprehend languages for the caster to circumvent this. A Familiar can only deliver its caster's touch spells.
Does comprehend languages work through a Familiar?
There are two situations where this would work through a Familiar. Remember that sight and sound, as well as special senses, are shared with the caster.
Important note: The caster must spend an action every round in order to maintain the reception of the Familiar's senses. If the caster cannot take an action or is otherwise forced to use a different action, then the caster cannot comprehend languages through the Familiar until the caster again takes this action. The duration of comprehend languages is one hour, so this should normally not be a problem in a safe area.