Backing out a merge - consequences?

[Tom Udale]

Greetings,

We have a situation where a feature branch was inappropriately merged 
(and pushed, of course) into the default branch.

I have on my local machine run

hg backout -r 1234 --parent 1233

which has dutifully put my local repo back at the state of rev 1233.

My concern however is what happens when I eventually do want to merge 
this feature branch into default?

My (hazy) understanding of the merge process is that it looks back to 
find changes since the last merge.  I assume it does not know that the 
backout effectively nullified the merge at 1234 and therefore it should 
look back to the root of the feature branch in order to determine what 
to do.

Is this a real problem or am I not thinking right?

Best regards,

Tom