I searched through WMS options and the forum as well but found nothing about subtitles' style tags.
For example SRT format supports BOLD, ITALIC etc. but the style is not applied.
Style tags are visible as subtitle text instead.
Tags <b>BOLD</b>, <i>ITALIC</i> and subtitles module removes tags.
How srt-tags help the purpose of subtitles?
SSA, ASS subtitles can be rendered with libass module (Settings - Devices - choose a device - Settings - "Files, subtitles" - turn on "Use external subtitles module ssa, ass").