This is an option that can be disabled in the config (custom font engine), but turning it off does not always resolve the issue. When Optifine and and Modular Powersuits are both installed, the icons used by Powersuits in the Power Tool selection and in the Power Armor Tinker Table appear to be replaced by pieces of the Tinker Table's specialized font. There is a known major compatibility bug between Optifine and Modular Powersuits (for MC version 1.5.2), which appears in the Unleashed, DW20 1.5.2, Tech World, and other packs. You can edit the configs with the F9 key as usual, just the names and chat bubbles will not show above the players name.
Also, a quick side note would be that after installing this you cannot use VoxelPlayer. This guide is meant to be as simple as possible, if you follow all of these directions to a T then you should be up and running OptiFine just well, fine. Introduction to installing OptiFine on FeedTheBeast. This article is part of the Feed The Beast Wiki's Tutorials section.