If you're playing with SWMH, yes.
Admittedly, we should've been more clear about this.
Technically, though, going forward each user has now been given the ability to keep track of the version numbers of the mods they use. It's in their installed mod folder (usually "Historical Immersion Project") as
version.txt. It contains the mods you selected while installing along with their versions and their release dates (plus an overall release date for the total module package + installer itself used to compile your specifically customized modpack).
Versioning semantics depend upon the mod. For SWMH, their versioning seems to be somewhat arbitrary based upon how big they think a change is, but that's because basically
every new SWMH release is going to be savegame-incompatible; after all, it's a map mod, and every map change besides localisation fixes will break save games. This is why SWMH has a slower release cycle than PB or VIET.
PB's versioning scheme is X.Y.Z (major, minor, and patch). Common to a lot of software projects, this version scheme has the following simple compatibility semantics: any versions of PB with the same X.Y component are savegame-compatible. When we have to break past saves, we increment Y, and reset Z to 0. Sometimes, we will increment the minor version (middle number, Y) even when the changes were still savegame-compatible if they were big enough in scope, but we will never break save games without incrementing the minor version (on our own-- if another mod you're using does, then you're SoL). All other changes, pretty much no matter how big, just increment the last number (patch), which is why it can grow pretty large.
All that said, we ought specifically include a big, bold note about any of the HIP mods being savegame-incompatible from the previous HIP release in the announcement. Ideally, we would also version the whole of the HIP package (even if you're not using the mods that are breaking savegame compatibility in it) in a X.Y.Z manner too. Z, the simple "guaranteed compatible release" number, increases once a week or so with every release no matter what, and Y is increased whenever any single one of the mods that the installer supports breaks its savegame-compatibility, whether or not it actually affects your particular mod combo. This means it will "false alarm a fair bit" more than it would if the whole thing was a single, monolothic mod that didn't support individual selections. However, it'd be an easy way to compare/tell at a glance that you should be wary and look for an incompatibility note related to a mod you use in the package before blindly installing.
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