This question is probably beyond the scope of just TeX, but certainly interesting to many.
When referencing a figure, a lemma, or an equation in a paper, is there a general rule of whether or not to capitalize the respective identifier, i.e., whether to write
[...] as in equation (3) [...]
[...] as in Equation (3) [...]
This is essentially the question if "Equation (3)" is a proper noun, or rather merely a description (much like "page 3" which I suppose everyone would agree on not to capitalize).