Fr Hunwicke's Mutual Enrichment is not a blog that can be usefully skim-read. His articles are not long, but they repay more close attention than those of the "5 reasons why Pope Francis didn't really say what everyone thinks he said" genre.
When I find time, as I have just now, I read a number of his posts in sequence. It is always a rewarding experience for me, especially since quite often he tackles something that I have wanted to say but not found the time, and writes on it with erudition and wit. During the past week, we have had, among other things, a discussion on whether Muslims and Christians worship the same God, a gently provocative piece on the lack of Latin among the clergy, and an important post arguing for baptism sub conditione for Anglican converts whose only evidence of Baptism is a certificate.
A baptism certificate was formerly regarded as sufficient, since baptism "according to the rites of the Church of England" is certainly valid. What is now uncertain is how often baptisms are conducted according to a rite that is not approved by the Church of England, specifically, baptism with the form "I baptize you in the name of the Creator, and of the Redeemer, and of the Sanctifier." Baptism using such a form is certainly invalid: the Congregation for the Doctrine of the Faith in 2008 answered a dubium on the matter, saying that persons baptised with such a formula have to be baptized in forma absoluta (that is, not conditionally.)
We must pick a careful path through doubts. Since the practice of using an invalid formula is certainly used in some places and is becoming more common, it is, as Fr Hunwicke says, no longer safe to assume that a baptism is valid simply because it has been carried out in the Church of England.
Sometimes we have other reasons to assume that the baptism is valid: one might know the local vicar, and know that he would always use the proper form (that would be true of my own Anglican neighbour) but we are not usually looking at certificates issued by the local vicar. The convert himself might be able to give assurance that the Rev Blenkinsop of St Mildred's in Thrampton was a sound man and would not have used an invalid form. In such cases, there is no need for conditional baptism.
But without such further evidence I agree with Fr Hunwicke that the doubt that now exists makes it necessary to baptise many converts conditionally since there is a reasonable doubt about the validity of their baptism. If on the other hand, there is evidence that the convert was indeed baptised by a feminist who used the invalid formula, then the baptism was certainly invalid and the convert must be baptised without condition, as the CDF laid down. In modern practice, such a convert would be a catechumen and not a candidate.