Melding items should increase their item level.

[Allyrion]

I will say it again. Gearscore should be calculated by a weighted sum of item stats, such as defence, magic defence, primary stat, vit, etc. NOT item ilvl.

The item level of a gear determines its stat budget and is distributed according to the stat weights. All 90 gear has an equal budget, so it is essentially the same as the sum.

I agree with the OP though. Penta melded HQ crafted piece is around ilvl 80 and should be treated as such. It would help if the UI reflected as such.