Probably due to the "#n" text in remixed dweets, people have picked up the convention of referring to other dweets with the #n syntax. Some ideas:
Change the remix text to say "remix of d/n by username" or even "remix of d/n by u/username" (and maybe make the d/ and u/ parts slightly faded out) as a hint to users on how to refer to other dweets/users -- but that might look ugly
Also accept the #n format as a way to link to dweets -- this should be a problem for future #tags since tags will very likely not be numeric.
Probably due to the "#n" text in remixed dweets, people have picked up the convention of referring to other dweets with the #n syntax. Some ideas: