As A.Ellett says, ▽ in this context is used as (in-line) bullet points. Although ・(中黒 {なかぐろ})is the most commonly used for this purpose, the ▽ symbole ("down-pointing triangle") is sometimes used in news articles. I think that it is common only in news articles, and feel that it's more often used to list things from which the reader wants to find one item, rather than read through all the information.
For example:
I wasn't able to find out why and when this symbol is preferred. My speculations are: (1) bullet-point is also used for separate words (e.g. ダ・ヴィンチ da Vinci / 月・水・金曜日) so maybe confusing depending on the context (2) ▽ stands out more, so it let the reader skim through the text quickly to find the information relevant to them.
I also noticed that some of the usages lack the first bullet (the 3rd and 4th listed above), but the meaning stays the same. Think of it as <ul><li></li></ul>
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Edit: ▽ and ▼ is interchangeable. @sundowner provided an answer from レファ協 that sufficiently answers this question (see the comment below). For completeness, the「新聞や雑誌の縦組コラム」 they refer to in the answer looks like this or this.