Ghodium hydride and its OH/X later boosts can increase how much 'upgrade' you do, without increasing energy cost. So 'maybe' if you had a 14W single creep w/ a boost it could go over the 15 cap? That might be what was meant by the increased limit, as smokeman said, (and noted by effect in the RCL 8 snippet there) power-creeps can increase this limit.
The 15 e/t cap is strictly on the amount of energy put into the controller, before any applied boosts. So if you're putting 14 e/t with boosts on one creep, you can only put in additional 1 e/t regardless of boosts.
And yes, there are now power creeps that can raise this cap.
Side question: How do i underline?
You can't underline in markdown (which is what the forum uses).