Guessing they meant "I have never read" and not telling you to "never read"

"Read" is a particularly unlucky verb for this because its past participle and imperative form are written the same way. Most other English verbs wouldn't have this particular ambiguity.

"Never eaten a Carolina Reaper pepper, but I'm looking forward to my first time."

"Never eat a Carolina Reaper pepper; you'll regret it."

Wiktionary has a few dozen irregular verbs that could produce an ambiguity like this one:

https://en.wiktionary.org/wiki/Appendix:English_irregular_ve...

"Never miscast Magic Missile ..."

"Never shut a door on someone's finger ..."

"Never preset the thermostat to 90 °F before going on vacation..."

"Never put an irregular verb in a position where readers might interpret it ambiguously..."

("... but there's a first time for everything, I guess" / "... you won't be happy with the results")

I find myself writing like this all the time. I omit the 'I', writing it like I say it.

Then I read back my own words and invariably insert the 'I' as I realise it doesn't make sense.

In this particular instance you'd have to disambiguate with "I have" or "I had", I alone would mean the wrong thing.

That's a participle with an elided subject and helper verb, not an imperative. In spoken English the difference in pronunciation makes it obvious.