The signs_lib signs (in the default:* namespace) always show text facing south, floating if sign is not facing south.

:edit: This only affects classic for some reason. Note that the text itself is an entity, so there may be an issue in classic with setting entity, or a breaking change in the engine which is assumed by signs_lib (The issue doesn't occur in Finetest). Also note that the issue doesn't occur in the zahyest world, but the default and signs_lib are identical to the tested copy other than spacing and some additions such as mese post, multiply_texture, and other unrelated additions.

[ ] Only south-facing signs work (player faces north since the sign you place faces you). Facing any other way fails.
[ ] Using the screwdriver on the sign doesn't rotate the text along with the sign but should.

affected nodes

The player can craft two wall signs that are affected. They transform into the subtypes listed under them below depending on whether they are placed on top of or on the bottom of a node rather than on a wall. All 6 nodes are affected by the issue.

[ ] default:sign_wall_steel
- [ ] if you place it on ground, it becomes default:sign_steel_yard
- [ ] if you place it on a ceiling it becomes default:sign_steel_hanging
[ ] default:sign_wall_wood
- [ ] if you place it on ground, it becomes default:sign_wood_yard
- [ ] if you place it on a ceiling it becomes default:sign_steel_hanging

All nodes listed above have the issue (tested in bucket_game 211107c).

Reproduce the issue

/giveme NODENAME 2 where NODENAME is any listed above. Only 2 kinds need to be tested, since the other 2 in parenthesis are generated when you place a wall sign on the ground.
face East, North, or South (Note: signs face you, so the sign's facedir is opposite which is correct)
place 2 signs as follows:
- wall sign: place on side of glass preferably so you can see better where the text will go if it will go somewhere wrong
- ground sign: place the sign on the ground and it will become one of the "yard" nodes listed above which also have the issue
- ceiling sign: place the sign on a ceiling such as pointing to the bottom surface of a tree branch or any other node (chains appear on the sign to show a visual connection)
right-click the sign and type (at least 4 letters or so so you can see it if it gets rotated wrong)
repeat these steps only once for each point under affected nodes (doing these steps for each of the 2 will generate the 6 different nodes since the steps include ground, wall, and ceiling placement)

Up-down facing sign failures

The following nodes don't show text on them when they are placed on the ceiling or floor, but work in all other cases:

locked_sign:sign_wall_locked

Signs known to not have the issue

all other signs work fine apparently, including legacy_signs:*

Related issues

[ ] #626

It can be solved in one of two ways: in minetest/src/script/lua_api/l_object.cpp change:

int ObjectRef::l_set_rotation(lua_State *L)
{
-    NO_MAP_LOCK_REQUIRED;
-    return 0;
+    // ^ This is a ~2019 MT5 feature, so above stub was the former code.
+    // code below is from Finetest:
+    NO_MAP_LOCK_REQUIRED;
+    ObjectRef *ref = checkobject(L, 1);
+    LuaEntitySAO *entitysao = getluaobject(ref);
+    if (entitysao == nullptr)
+        return 0;
+
+    v3f rotation = check_v3f(L, 2) * core::RADTODEG;
+
+    // entitysao->setRotation(rotation);
+    // ‘class LuaEntitySAO’ has no member named ‘setRotation’ in MT4, so:
+    entitysao->setYaw(rotation.Y);
+    return 0;

or (backward compatible): signs_lib.spawn_entity function

in signs_lib/api.lua

-        obj:set_rotation({x = pitch, y = yaw, z=0})
+        if obj.setyaw then
+            obj:setyaw(yaw)
+        else
+            obj:set_rotation({x = pitch, y = yaw, z=0})  -- exists in some version of classic but is a stub (no op)
+        end

Poikilos / EnlivenMinetest