This sort of statement represents one consequence of the aforementioned bad precedent.
Are checkpoints good now?
So far in this discussion, and in a thread that has forked off, I think 3 cases of implementation aspects have been mentioned that under certain circumstances result in the validity of chains changing:
* Buried softforks (by simplifying the activation rules for certain rules)
* Not verifying BIP30 after BIP34 is active (since only under a SHA256^2 collision a duplicate txid can occur)
* The existence (and/or removal) of checkpoints (in one form or another).
None of these will influence the accepted main chain, however. If they ever do, Bitcoin has far worse things to worry about (years-deep reorgs, or SHA256 collisions).
If you were trying to point out that buried softforks are similar to checkpoints in this regard, I agree. So are checkpoints good now? I believe we should get rid of checkpoints because they seem to be misunderstood as a security feature rather than as an optimization. I don't think buried softforks have that problem.