I really like Morphead's Calibri Shower, specifically the standalone version as I can use it to make custom "modular" showers, and it has a classier aesthetic than the other standalone showers I can find. However, it seems to have been cloned from the cheap shower, so even though the attributes have been edited to be better, it still gives the "Cold Shower" moodlet.

Is there a flag or value I can change in S3PE to make it so this shower can no longer give this moodlet? I'm comparing the object data to that of an expensive shower and can't seem to spot a meaningful difference, especially not where I would think to look (MoodletGiven and MoodletScore). Any help would be appreciated, as I'd really love to be able to use this shower without that pesky negative moodlet.

The OBJD values are just about what information is displayed in the catalog, regardless of whether it's accurate or not.
How the object actually behaves is all in the script, which is applied in the OBJK.

In S3PE, right click the OBJK and choose Edit OBJK.
In the section for a script string, replace it with Sims3.Gameplay.Objects.Plumbing.Mimics.ShowerLoft (this is the script of the expensive base game shower).
Save, commit, save the package, and you're done

Existing objects placed ingame may need to be sold and placed again for the changes to take effect.

Amazing, thank you so much! I did see that line in there and thought it might be the key but I wasn't sure how it worked so I didn't want to mess with it without being sure.