<…> Isn't it Against forum rules to use multiple accounts? I saw lot of people tagged for using multiple accounts.
Not having multiple accounts per se, but using them to participate in the same campaign is considered cheating (they can participate in different campaigns simultaneously), as is sending merits from one to another. Still not bannable, but if one account goes down for breaking some rule, so do all belonging to the same person.
This reminds me (vaguely) of the dialogue in the first episode of The Mandalorian, when The Mandalorian teams-up with a droid:
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00:30:24,658 --> 00:30:26,028 Mandalorian: We split the reward.
00:30:26,827 --> 00:30:28,287 Droid: This is acceptable.
00:30:28,370 --> 00:30:32,330 Mandalorian: Great. Now let's regroup, out of harm's way, and form a plan.
00:30:32,416 --> 00:30:35,286 Droid: I will of course receive the reputation merits associated with the mission.
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Just that in this case the Mandalorian and the droid wold be two accounts puppeted by the same person.