sign/compare/maybe/is/rectform inconsistencies

kill(all);
done;

sign(x);
pnz;

compare(x,0);
unknown;

maybe(x>0);
unknown;

rectform(x);
x;             /* x is assumed real by default. */

declare(x,complex);
done;

sign(x);
pnz;

compare(x,0);
unknown;

maybe(x>0);
unknown;

rectform(x);
realpart(x) + %i imagpart(x);

assume(x>0);
[x > 0];

sign(x);
pos;           /* assume seems to have forced imagpart(x)=0. */

compare(x,0);
>;             /* assume seems to have forced imagpart(x)=0. */

maybe(x>0);
unknown:                        /* ???? */

rectform(x);
realpart(x) + %i imagpart(x);   /* ???? */