Checking the level of Lydia, whom I got at level 8, and she is now level 15.

I took some free tests to find out my direction

how do you check a followers level?

open the console with the tilde key (`), click on the follower, type getlevel

Followers always have been able to level. It's just that their skills, health, magicka and stamina won't change even though their level has increased.

You need to use "getav" command to check these values.

And as far as I know patch 1.3 mainly fixed the problems caused by 1.2. Follower leveling issue is not addressed.

I wish I could check on a console, but Ive had the same follower for about 15 lvls and so far he's keeping up in combat just fine. (too say the least)

I have of course heavily upgraded he gear.

Seems like it would be a huge oversight for them not to lvl with you (didn't they in F03), as naturally a lot of players are going to want to keep the same follower through out their game, and that would basically force you into getting a new one.