"Worst case", I said it is time to stop using uppercase font on drawings. Let's continue that discussion, this time looking at specifications. Not that we should be using one set of rules for drawings, and another for specifications; the same rules should apply to both. With a few exceptions, text should use sentence case - capitalizing only the first word of a sentence and proper nouns. This seems reasonable, but, as we will see, it rarely happens.
Let's start with the exceptions. Section titles, Part titles, and article titles typically are presented in uppercase, and though it's not necessary, it has little effect on readability or comprehension, as these elements have few words. In addition, we're accustomed to it, as it's common in many other publications to use uppercase in those locations.
Beyond that, however, use of capital letters is unnecessary, and can be misleading.