Altars only display the b/u/c status if they're co-aligned.  If you go dropping items on altars that aren't your alignment, the deity is annoyed with you and curses your item.  So, as you guessed, four in a row isn't bad luck in your case.

Each deity has their own list of likes and dislikes. For the good deities, these are things like attacking friendly creatures, cannibalism, grave robbing, and desecrating good-aligned altars.  The neutral-aligned deities are less consistent (Vedere has similar restrictions as the good three; Voros only dislikes graverobbing and desecrating neutral altars; the Trickster relaxes the restriction on attacking friendlies), and the evil deities are the most permissive.  They just don't like you desecrating their altars.

Humans don't start with literacy by default.  The only race that does are gnomes.  There's a quest in Isen Dun that'll grant it.  I probably should have added a similar one to Carcassia.  I'll look at doing that for the next release.

I just double checked the code, and the behaviour is:

- Drop on aligned altar: bless (burns some piety)

- Drop on non-aligned altar: curse

You can identify item statuses via scrolls of identify, or by playing a PC with the Lore skill (merchant, minstrel, pilgrim, sage, wizard, witchling).  The Lore skill has a one-time chance to identify an item on pickup.