[RPG] After you attune to a cursed magic item, are you aware that it is cursed

I don't recall anything in the existing manuals that allows a "simple" way to detect curses. I believe they were trying to make curses more interesting to play. So, from the rules view there is no easy way to know if an item is cursed except by trial an error (It adds drama!).

An easy way out would be to house rule a curse-detecting clause to a spell (identify, for example), in the sense that it would detect the negative effect of using the item.

Other ways are to hint it to player. Lore, like you said, is a good approach. Legends, rumors, hystorical records could point to a certain object being cursed. Maybe there's a warning in the item's resting place or the PC sense something "not right" when they touch it.

The fact is that by allowing to easily detect a curse it cuts off a bit the point of it being cursed. Curses are meant to be narrative devices. If you want to avoid the hassle you can always reduce the "curse" to negative traits or flaw like the DMG suggest in the artifact section.

The most likely interpretation is that if an item states that it cannot be removed without remove curse, then it cannot be removed without remove curse.

Reason 1: Specific beats general

The principle of "specific beats general" is stated as follows in the Rules Compendium (2007):

A general rule is a basic gudeline, but a more specific rule takes precedence when applied to the same activity. For instance, a monster description is more specific than any general rule about monsters, so the description takes precedence.

While dispel magic in general can suppress magic items, specific cursed items can override this with specific properties.

Reason 2: Item descriptions

Cursed items are usually explicit when naming the spells which will counter their curse. For example, consider the Gauntlets of Fumbling (emphasis mine):

Once the curse is activated, the gloves can be removed only by means of a remove curse spell, a wish, or a miracle.

The item text is very specific: the item cannot be removed, except by one of the three named spells. It does not say what happens when you try any other method or spell, only that it will fail.

Note that this particular curse only prevents removing the item. It may still be possible to temporarily dispel a cursed item's other magical properties.

Reason 3: Primary source rule

According to the D&D 3.5 errata, when two rules come into conflict, the Dungeon Master Guide takes precedence over the other rulebooks when it comes to rules for magic items and cursed items, since the DMG is the primary source for those rules.

(However, this is not a watertight argument, since by the same token, the Player's Handbook is the primary source for rules on spells, such as dispel magic.)

Reason 4: Adjudication by similar rules

The Dungeon Master's Guide gives the following advice to DMs adjudicating ambiguous situations:

When you come upon a situation that the rules don't seem to cover, consider the following courses of action:

• Look to any similar situation that is covered in a rulebook. Try to extrapolate from what you see presented there and apply it to the current circumstance.

In other words, it's reasonable for a DM to interpret an ambiguous rule by inferring a solution from other related rules. The closest similar situations I can find are as follows:

• The spell bestow curse says that "the curse bestowed by this spell cannot be dispelled". This supports the idea that curses are specially resistant to dispel magic.
• The Loadstone, a cursed item, will return to your possession even if you destroy or throw it away. This suggests that even if you temporarily outsmart a cursed item, it will return.