Non-language characters such as "♥", "★", and "*", sometimes found in advertisements or logos, are not the common English usage and, hence, should be avoided.
However, when the usage of the symbol convey more than one text readings, such symbols should be kept for accuracy.
Examples of the rationale:
- We Love Katamari not We ♥ Katamari because ♥ in this title only meant love.
- Lucky Star (manga) not Lucky ☆ Star because ☆ in this title is purely stylistic and do not convey any meaning.
- I ♥ Huckabees should be kept because the producer intentionally used the ambiguity of ♥ to convey both the meanings of love and heart.
Also see Wikipedia:Naming conventions (common names) and Wikipedia:Naming conventions (use English).