原文:Since the scanner is cordless, its battery is its only source of power,
and since the scanner is intended to be handheld, the weight of the battery is
limited by "what" an average user can comfortably hold up.
我想请问一下，如果把What拿掉，在文法上是对的吗?感觉这边的What只有强调的作用。
那假使只有强调的作用，在中文上该怎么翻比较好呢?

拿掉的话会是错的；介系词(句中的by)后面要接名词而你也不能说那个by接的名词是an user...(略)