It's well known that in custom spells/enchantments, the order of weakness effects matters a lot.
But while experimenting with custom spells, I notice that the spell effects are mostly applied according to alphabetical order. That means, for example, Absorb strength always applies before Drain, and then Fortify, when they are all on touch, no matter how exactly those effects are placed in the spell.
Of course, it doesn't matter very much for beating the game. But when it comes to some minor mechanics, it can cause confusion, as one spell may work in the English version, but fail in the French/German version of the same game.
Recently, I found an interesting spell combo that works in English but not in German:
Burden 100 1s + Feather 100 4s + Weakness to Magic. It results in a negative encumbrance after 1s. Spam it several times to accumulate a huge negative encumbrance.
Feather 3 120s. Reset the negative encumbrance to zero, equivalent to a powerful Burden effect but super cheap. After the Feather effect of Spell 1 wears off, the target is overburdened and held for 2 minutes by Spell 2, with quite low cost.
The key point is that in Spell 1, Burden is applied before Feather. It works this way in English and French. But when I tried the German version, Feather and Burden are in reverse order, so they can't provide the expected negative encumbrance.
Noticed another example years ago: adding all the Bound Weapon effects into one spell. Only the first applied bound weapon appears in hand, and the specific weapon varies by language.
Thankfully, it doesn't seem to have the same problem in remaster. No matter the language, the spell effects always follow the order in English.