(Copy Editor and mathematician speaking)
I, for one, allow these mixed constructions when editing the articles. I do know that it is not the best grammatical style, but not everything in math is easy to put down in proper English grammar. The two rules of thumb I use for these boundary cases is: Is the text clear to the reader? Can you easily make it grammatically correct?
For instance, the sentence "For matrix A, the equation rank(A) ≥ 5 holds." is cryptic and long. A better option might be "For matrix A, we have rank(A) ≥ 5." or "Matrix A satisfies rank(A) ≥ 5." I would be fine with "Matrix A has rank at least 5." However, this gets complicated if you have more such expressions in a row, like in:
... which is defined as a non-real algebraic integer in modulus >1 whose Galois conjugates except its complex conjugate are in modulus <1.
... which is defined as a non-real algebraic integer in modulus greater than 1 whose Galois conjugates except its complex conjugate are in modulus less than 1.
I prefer the first option. This went through the AMS language editorial, as far as I remember, without any problem.