[cenamus]

Don't know how applicable it is in regards to vowel marks, but similarly in online conversation Czech people often leave out all diacritic marks (so no čšťďřňůúáéíýó). This used to be completely incomprehensible to me, until I had enough knowledge to read "normal" Czech text with relative ease.

So it seems to make a lot of sense to learn with that aid and later transition to no vowel markings (or reduced / the normal amount)