Not a standard per se but practical advice.
Null text is that text that is an empty string, or nothing but "white" characters -- tabs, spaces etc. It can exist in drawings because some [explitive deleted] operators "delete" text by bring it up in the editor and leaning on the space bar. While it sounds bogus I have seen it happen for years and it never ceases to amaze / annoy me, with extreme cases exceeding 70,000 null text entities! I wish I were joking! Symptoms are slow loading given content, zoom extends that do not make sense etc.
Quick test: Turn QTEXT on and then do a zoom extends; each space or layout tab. Little freaking boxes all over the place!
Thoughts?