Q: How do you say, “Thank you for accepting me”?

A: I frequently see comments in this form:

a. Dankon por akcepti min.
b. Dankon pro akcepti min.

In Esperanto usage, pro is not followed by an infinitive. Sentence (b) is incorrect. If you want to use pro, you have to use a form like:

Dankon pro tio, ke vi akceptis min.
Dankon pro la akcepto en la grupo.

The preposition por can be used with an infinitive, but generally with the meaning “in order to X.” So for example,

Mi aĉetis farunon por baki panon.
Mi pagis multe da mono por havi ĝin.

So my advice is to avoid both (a) and (b) above. They are attempts, I think, to model the English structure “Thanks for accepting me.” But that particular structure doesn’t exist in Esperanto. Another option in addition to the two I gave above is:

Mi dankas vin, ke vi akceptis min.

Is there an absolute logical reason why pro can’t be used with an infinitive, or why por before an infinitive means “in order to”? No. But this is a good example of how usage is one of the predominant factors in how Esperanto is actually spoken.

When you learn Esperanto, you become part of an established speaker community, and there are usage-based rules within that community.