Jordis will sometimes disappear for no apparent reason. She will be found at Proudspire, wearing her original gear. Ask her to trade equipment and all the gear she had when she left will be in her inventory. Remove one item and give it back and everything is reequipped.
Jordis acts as a merchant if the Dragonborn marries her but only in the marital home. She buys and sells all categories of merchandise.
Jordis will not use some bows, even though they may be superior to her base weapon. She seems to prefer Ancient Nord weapons. She will wield the Gauldur Blackbow, but will not use the Nightingale Bow, even though it is far superior to her default Hunting Bow.
When marrying her, she'll ask whether to move into your house, or her house. Either choice will be your current house.
If given an ebony shield, Jordis might think it is a weapon. She sheathes it and uses it as a weapon while the actual weapon stays sheathed. The effects of this have not been tested in battle.
When given Necromancer's Robes to carry, they cannot be removed later. The message, "You cannot remove your teammate's starting armor," appears.
Jordis may occasionally treat you as an outsider or trespasser when you enter Proudspire Manor even though you're the owner. This can be fixed simply by exiting and re-entering the house.
If you marry her, she may disappear during Maramal's speech. To fix it, continue your travels away from Riften for some days and return to the temple of Mara. She will be there and will speak to you about choosing a new house to live in. Sometimes she may be found on the upper wooden catwalk near the Riften main gate, accessible through the back of the row of houses.
If Jordis is replaced by a Companion follower for the Companion v Silverhand storyline, when you go to get her back all her inventory will be gone.
If a former follower is killed by you accidentally or purposely, their body will appear if you attend the wedding with Jordis causing the task "attend your wedding ceremony" to fail. Jordis will say things like "just leave" and you cannot get married. To fix this, move the body to the basement then ask both Jordis and Maramal to have another wedding.
If married to the player and killed (either accidentally or purposely) then resurrected and remarried, she will say that she has decided to open shop. However, you cannot shop there, nor can you receive your share of the earnings.