[Arion]

@Angelina

Thanks! I'll study the code and (I hope) make a definitive solution.


Edit.

I don't know how, but I found a solution. Luck, I guess.

I only changed all returns to PLUGIN_CONTINUE, added this to plugin_init():
register_message (get_user_msgid ("SayText"), "avoid_duplicated")

and in function avoid_duplicated, this:
return PLUGIN_HANDLED

And voilà! Prints in chat (once), server console, HLSW, and doesn't interfere on other plugins anymore. Want more?