Introduce a new `_sanitize_mentions` method in `BotHelpersMixin` that deduplicates and removes self-mentions from text, using a compiled regex for `@handle` patterns. Apply this sanitizer before the 2000-character truncation in both `engage.py` comment posting and `social.py` reply posting to prevent duplicate or self-referential mentions from being cut off mid-handle. Additionally, fix profile URL parsing in `social.py` to strip trailing path segments, and refine `LLMClient.clean` to handle asterisks and underscores more precisely without breaking adjacent alphanumeric characters.