More odourless observations...
3beltwesty, yes... I find this interesting too! It makes me realize how every single 1 of us can develop different opinions based on several experiences... at this point I guess I can only assume that we're all saying the right thing and stating our truths the way we see them, as I'm sure you'll agree, there are many scenarios out there (even some evidence in some instances) which provide plausible conditions for the existence of mould or bad smells in general. You never experienced any mould issues with your Westy... but maybe you wouldn't have any problems with a new American FL either... who knows... well, it's my understanding you also have a modern LG American FL... only time will tell whether you'll have the same feedback in terms of mould freedom as the Vintage Westy.
Admittedly, everyone, I still fail to see any potential smell issue being directly associated to liquid detergent or powder detergents for that matter... and I feel the same about fabric conditioner... and as for this mixing with detergent it shouldn’t be so likely as it normally enters the washtub on the last rinse when the load is already rid (well... partially rid in the case of a poor rinse performance) of the detergent solution! Personally I've never had any problems with fabric softeners, I'm an absolute fabric conditioner addict... well, my clothes are

Beside the joke I remember when I was living with my parents as a teen... all hell would break lose should the entity responsible for doing the laundry forget to add fabric softener to the wash!
At times when I find a build up of scum left behind by the softener within the detergent draw it doesn't usually have a bad smell... it usually just smells of fabric softener. A few years ago I found myself cleaning my parents washer's detergent draw and I came across something rather staggering... well, the softener compartment had an extra compartment below the usual plastic grille within the drawer itself (I was aware of this... but apparently I was the only 1) which hadn't been taking out of its slot for at least 13 years... this was configured in such a way that it'd look as if it was part of the drawer rather than being a separate piece. When I lived with my parents I used to take care of all washing machine related maintenance operations including cleaning... but having left home, this tricky particular had gone unnoticed till it was confronted by its original carer (me). Of course it was a job an a half to take these little vessels out of their slot (there were 2 actually: 1 for the bleaching agent but never used)... and when I did get them out you can imagine the amount of gunge, scum, sticky substance, encrustation... you name it... that was thriving underneath: it did not smell though... I assume it wasn't mould.
Last thing... many people have mentioned excessive use of detergent (not just in this forum) but can it be just the opposite? Too little detergent can just contribute to allow build up of bacteria and bad smells. I thought it would even make sense if there was a crud formation in a top loader cos' the detergent used in such a large quantity of water might have not been enough on occasions perhaps if a particular load of laundry was dirtier than usual and required a higher amount of detergent. Now I'm mentioning this and... I recall using too little detergent during my 'cold wash freak' days as I figured less detergent would dissolve easier in cold water: don't pick on me now! So there you have it... it might very well be that! When I decided to take charge over the musty smell in my washer last year I obtained the best results when I used a higher dosage of detergent (as well as the use of warmer temperatures as I mentioned in an earlier comment). Having said that my situation might very well be isolated from the rest of the experiences discussed here as the odour I came across was rather faint and undetectable from the others around here... it's mostly me and my obsession for sniffing everything! But I was right... I could smell it, but not anymore now!