Can something be done to improve the recommendations?

[Oobaka-san]

It may be a stupid request, but the recommendations on this site are often laughable, to the point that I suspect most people who make recs don't even read what they're putting recommendations on. This is particularly bad in the mystery genre, an area where I've also had to give up on the genre tags as the genre tag includes huge numbers of series with little to no mystery in them, or with just one arc where there's some search to figure out who the villain is, yet they're still called "mystery" series, cluttering the list and making it harder to find stories that actually are centered on mystery (I think I suggested it before, but a "primary genre" or something like that might be useful to deal with this, as well as with romance which you could add to 90% of series as most series have some romantic aspects).

For example, take a mystery series called Shion no Ou. The story's about a teenage girl's efforts to become a major pro at the game of shogi where normally the strongest female-league player is worse than upper-level students aiming to become pro in the main league, all the while torn by the traumatic memories of her parents' murder when she was five. Along with the sport element as she works to improve, much of the story focuses on the struggle to find the killer despite a surprising lack of clear evidence. There are lots of interesting characters, including another girl who's working to gain recognition in an environment where people normally see girls as "cute" at best, a boy who cross dresses in order to compete in the women's league and make easy wins so he can pay his dying mother's hospital bills, a young man who suspects his beloved's death was connected to the murder mentioned above and engages in his own independent investigations, and several pros with their own situations and objectives. What do all the recommendations have in common with the series then? Psychological elements? Murder mystery? Shogi? Nope. Cross-dressing. Even worse is QED, a series that's mostly an episodic series of murder mysteries solved by an athletic JK and a boy genius, which has only one mystery in its recommendations while most of the remainder is sports series for some incomprehensible reason, with one or two basic slice-of-life stories scattered in between.

These recommendations are supposed to lead fans of a work to similar works or works that people who specifically liked that work could seriously expect to enjoy in a similar way, right? As is, this seems to have failed pretty bad, at least in some places. Might not be noticeable for people whose main interests are mainstream stuff like Shounen battle or Shoujo romance, but if you're looking for some other genres it can be like looking for a needle in a haystack, a haystack made entirely by people thinking putting hay in the "needle" pile is helpful.

 

[Hicleric]

The recommendations aren't curated at all, from what I recall of the initial discussion when they first launched. There's some background logic (probably) related to tags that is refreshed every so often but I don't believe we've ever been granted a peek under the hood. Could be cover style and aesthetics for all I know

I would be interested in seeing utilization rate of this feature but I suspect it's not trackable and also quite low. I've occasionally found some interesting titles worth following up but as you point out, more often than not it doesn't produce actionable leads and I often just forget it exists.

 

[undeed]

I don't know how the recommendation list is actually selected,
but ever since the feature was first introduced, I immediately assumed that it's just displayed based on a similarity sorting of the tags listed for each manga.

So, all the recommendation anomalies you mentioned are very easy to explain.
The similarity likely only uses the simplest calculations like Jaccard, Pearson, or cosine, without any complex recommendation system that uses graphs and relationships between manga, let alone relationships with the readers.

For example, with QED you mentioned, the Pearson similarity value with everything that appears in the recommendation tab is >0.5.
Meanwhile, if you calculate its similarity with something like Hyouka or Master Keaton, the value is only 0.4.
Tho, the strange thing is, CMB manga value is actually quite high, so it should have appeared in the recommendation list too. It might just be because of the sorting process. idk.

And since the arrays being compared are quite long and sparse, (78 tags in total, I think?)
adding with the tag management process itself has been quite inaccurate from the start the similarity values end up being somewhat contaminated.
(which is why I've never trusted tags on MD since time immemorial),

It's okay for just a fun feature.
Just think of it like a more "guided" random manga list

It could be somewhat improved if some weights were applied.
I have also previously suggested implementing levels in the tag system, which could then be used as weight values.
But then it means that someone have to do some tinkering around to figure out the right weights for that.
And that's easier said than done.