I won't (at least initially) provide links to specific questions: if I'm later asked to, or you find them anyway, please be careful of triggering any "meta effect".
A question from October 2018 from a woman whose husband died just over a year ago has appeared on the front page of PF&M by dint of being "Protected" a couple of hours ago. Nearly two years ago (October 2017), another "old bereavement-related question" (originally asked in 2015) popped onto the front page because someone else provided a new (not very good, IMHO) answer. I answered that one before I realized that the original was so old.
In both cases, the person who asked the question has very likely already dealt with the issue they were asking about: answering such questions is unlikely to help them but will – if they are still active on PF&M – bring the bereavement back into their minds when they see the notification of a new answer. However, as PF&M is trying to be a "library of detailed answers to every question about money or personal finance", having such questions answered is part of our raison d'être, and we should be trying to help anyone else with the same problem in the future.
Answer such questions completely "as normal". Take the view that if the OP asks a question on PF&M about a bereavement, they accept the risk of being reminded of that bereavement at any point in the future.
Answer normally, but with a preface along the lines of "This may no longer be of help to the OP (and apologies if this stirs painful memories), but for anyone else in the same situation..."
Lock or delete such questions to avoid generating potentially painful alerts for the OP. Locking is probably more appropriate where there is at least one good answer; deletion perhaps more appropriate if there are no answers.
Something I've not thought of.