There were two incidents where aircraft entered dense ASH clouds at night.
...lets not go too far to under-state the risk.
There have been documented daytime 'incidents' involving damage to engines apparently caused by VA. Thankfully nothing involving any personal injury so far, most recently, the Finnish F-18 encounter - of which nothing much more has been reported. I don't recall reading what the visibility was at the time but I don't think it was at night. Presumably even military jet jockeys know not to fly through VA.
Also, lets not forget that this part of the discussion started with photos of a Cessna engine problem. This has already been quite thoroughly refuted by someone presenting themselves as a Cessna employee. Given the lack of any re-refutation in the original threads, this is now a Dead Letter. Why 'provenance' of a false rumour could be interesting defeats me. Maybe PBL should subscribe to the UK Daily Star for countless better examples that serve only to sell newspapers.