Why was this question closed? the right way to introduce a vivid recollection in English
The explanation there says:
Questions asking for someone to find and correct errors or improve the phrasing are considered requests for proofreading and are off-topic.
But I didn't ask there for proofreading at all! I just brought up an example, in which I usually stumble upon a similar situation and don't know how to express that thought of mine in English properly. The example I used was only for making my problem clear.
Besides, I used the tag "phrase-request". Using that tag is absolutely on-topic.
...memory of him how he once participated...
which, I hasten to add isn't wrong just slightly wordy, but then again it risks falling under writing advice and "style" which makes it off-topic.