I keep having this incredibly obnoxious problem where a parent will put a toddler in the high chair, but as soon as they see the toddler fussing (usually because the toddler is hungry) they'll autonomously let the toddler out and either set him/her on the floor or put him/her in his/her crib without being fed. Either this happens, or some other adult or teen shows up and wants to "hold the youngster" even though the "youngster" is still eating or waiting to be fed! Is there anything that can curb this autonomous action/keep people from letting toddlers out of the high chair?

I am using No Baby/Toddler Swarming

Do you direct that parent or teen to feed the toddler as soon as they have placed them into the chair? Play on slow, hit pause and click the fridge. I don't use toddler swarming and have no troubles. Also you can feed them on the floor by simply handing them a bottle or you can grab a few bottles and put them into the toddlers inventory and pull them out as needed.

Not an exact answer to your question, but as an alternative, you can also try Christianlov's 4-in-1 NPCs. His nanny does a grrrreat job of taking care of a kid's needs (unlike EA's unholy abomination), and is configurable too.

I realize I'm starting to sound like the adoring fanboy from Oblivion when it comes to that mod and author, but... yeah, I am.

There's also Pescado's nobabyharassment.

Do these two mods do exactly the same thing or something different, does anyone know?

They basically do the same thing but there are some differences between them. TwoJeffs says that the readme on no baby/toddler swarming explains exactly what the differences are.

It's something I see quite often in my game - it's not harrasment, or swarming - one parent puts the child in the high chair and goes to the fridge to get food or bottle. The other parent decides, at that very moment, to pick up the toddler in the high chair and play with him/her. I don'tt think it is a huge problem, but it tends to be annoying with twins! You can either try to feed both twins for hours or you can go for a bottle from the fridge. I normally just directed the parent/ sibling who has picked up the toddler to go and get a bottle from the fridge then. (And I have two fridges. Or three. Or four. One in the nursery if necessary ) Problem arises when it's a guest picking up the toddler, like family Sims will often do while visiting your Sim household. (Somethimes they will go and get a bottle out of the fridge). However - babies don't seem to die when they are a bit hungry, and somebody will feed them sooner or later.

What you have just described is what Pescado/TwoJeffs meant by harrassment/swarming.

I am using free will all time and TJ's mod was exactly what I wanted because it is still leaving parents and nannies and guests with autonomy. Pescado's mod is without autonomy. So I do not need direct them to take care of toddlers/babies. Also it states toddler/baby "being in use" already if one adult/teen is taking care of them. So others will not rush to get them too and will find something else to do. Nannies are much smarter too.

Thanks, all. I downloaded NoToddlerSwarming, so we'll see how it works.

By the way, is there a mod that makes adults actually throw away the bottles instead of just littering the floor with stinking, contaminated bottles?

Self-Exploding Bottles

http://www.simbology.com/smf/index.php?topic=10.0

I have that mod by Pescado - they still do it.

I have the same problem, Justpetro. I have the no baby harassment and no toddler swarming mods and people still dog-pile onto the toddlers constantly.

I think twojeffs mod and pescado's mod conflict with each other if you try to use them both. I'm using twojeffs version and my sims pretty much leave the toddlers alone. Though I also use cribs that toddlers can get themselves in and out of, snapdragons in my nurseries and use the sim blender to teach toddler skills instantly so there's really not much that the toddlers need the adults to do.

Okay, so now I have the one from Twojeffs only and I'm still getting random people piling onto the high-chair, particularly neighbors.

Try the mods by Squinge then. They're at insimenator.org. Maybe Squinge included the highchairs in his coding.