Learn Farsi: آنها حساب من را دنبال کرده‌اند.

To make the present perfect of a compound verb, you only change the 'light verb' part, which is کردن (to do). You take its past participle کرده and add the personal ending. For 'they', the ending is اند, giving us کرده‌اند. The non-verbal part, دنبال, just sits in front.

Why does the direct object marker را come after من instead of right after حساب?

The word را must come after the entire group of words that makes up the direct object. The object here isn't just 'account', it's 'my account' (حساب من). Therefore, را goes at the very end of that possessive phrase.

Does the word حساب mean a bank account or a social media account?

It can mean both, exactly like the word 'account' in English! You can use it for banking or for online platforms. Here, the verb دنبال کردن (to follow) makes it obvious they are talking about a social media account.

Is it possible to split دنبال and کرده‌اند and put other words between them?

Generally, no. In the present perfect tense, the non-verbal part (دنبال) and the conjugated light verb (کرده‌اند) stay right next to each other to form the complete compound verb. You wouldn't put the direct object or other adverbs between them.