There are different cases for this. IMO, people shouldn't:
a) Outright beg for merit.
b) Outright beg for post reviews via PM.
I do not think that we should instantly tag people who fall under the category 'b' (which is not the case with OP). However, if the user displays a pattern of asking several members for this, we should tag them IMO. What do you think?
Seems like a good idea, since like atleast in the second case they're putting in some effort to actually post decent content. Better than just outright begging for merit with no real rhyme or reason.